Chemistry: A Volatile History (2010–…): Season 1, Episode 2 - The Order of the Elements - full transcript
In 1869, a wild-haired Russian
chemist had an extraordinary vision.
He'd been struggling with
a mystery
that had perplexed
scientists for generations.
And for the very first time, he'd
glimpsed nature's building blocks,
the elements,
arranged in their natural order.
His name was Dmitri Mendeleev,
and he was on the brink of cracking
the secret code of the Cosmos,
what was to become one of man's
most beautiful creations,
the Periodic Table of Elements.
This is the story of those elements,
the building blocks that make up
the universe...
..the remarkable tale
of their discovery,
and how they fit together, reveals
how the modern world was made.
'My name's Jim Al-Khalili.
And ever since I started studying
the mysteries of matter,
'I've been fascinated by
chemistry's explosive history...'
Ho-ho! Brilliant!
'..I've discovered some
exciting elements...'
That's fantastic!
'..and I've seen how chemistry
was forged
'in the furnaces of the alchemists.
'Now I'm going to continue
my journey.
'I'll take up the quest
of the chemical pioneers...'
Well, my arm's burning up.
'...as they struggled to make sense
of elemental chaos
'and conquer
our fundamental fear of disorder.
'Could there be a grand plan
underlying the elements?
'I'll take part in some
volatile experiments...'
Now we're going to drop
in the potassium.
Wow, look at that! Wahey!
'..and witness some
fiery reactions.'
And I'll find out how the hidden
order of the natural world
was revealed in all its glory -
the order of the elements.
As a nuclear physicist,
I've spent a lifetime studying
the sub-atomic world,
the basic building blocks
of matter.
But to do that, I need to understand
the ingredients of OUR world...
..the elements.
Our planet was created
from just 92 elements.
The ground we walk on, the air that
we breathe, the stars we gaze at,
even us.
Our bodies are
entirely made of elements.
We now know the name and number
of every naturally-occurring
element in existence.
But 200 years ago,
those elements were only just
beginning to give up their secrets.
At the beginning
of the 19th century,
only 55 had been discovered,
from liquid mercury
to dazzling magnesium...
..and volatile iodine.
Scientists had no idea how many more
they might find,
or whether there
could be an infinite number.
But the big question was,
how did they fit together?
Were they random stars,
or was the elemental world born of
order and logic?
Solving the puzzle would prove
to be a daunting challenge.
And the first glimmerings of an
answer came from an unlikely source.
John Dalton
was an intelligent, modest man,
and he had one
very British passion - the weather.
He was born here
in the Lake District in 1766.
He was so clever, that
as a young boy, just 12 years old,
he was already teaching other kids
at a school that he set up.
Walking home, he loved watching
the weather systems
sweeping across the fells.
He was so obsessed that he kept
a meteorological diary for 57 years,
and every single day,
come rain or shine,
he entered his precise
observations - 200,000 of them.
Dalton was a quiet,
retiring man with modest habits.
He was a lifelong bachelor, with not
much in the way of a social life.
His only recreation
was a game of bowls once a week,
every Thursday afternoon.
He was certainly
a creature of habit,
and he might sound a bit dull.
But actually, Dalton was
an avid reader and a deep thinker.
Underneath his mild-mannered
exterior,
his head was teeming
with radical ideas.
Now scientists had recently
discovered something very important
about the way elements combine
to form compounds.
When they do so, they always combine
in the same proportions.
Dalton would have known that
table salt, sodium chloride,
is always made up of one part
sodium and one part chlorine.
So it doesn't matter whether the
salt comes from Salt Lake City
or Siberia, it's always in the same
proportion by weight, every time.
Dalton reckoned for this to happen,
each element had to be made up
of its own unique building blocks,
what he called
"ultimate particles", atoms.
It was a blinding illumination,
completely left field.
Everything, he suggested,
the entire universe,
was made up of infinitesimally
small particles.
The Greeks had hit on the idea
of the atom 2,000 years earlier,
but abandoned it.
Now, Dalton took up the baton
with his own theory of matter.
What Dalton was describing
was revolutionary.
He had struck on the foundations
of atomic theory,
foreshadowing research that wouldn't
be proved until a century later.
He proposed that there are as many
kinds of atoms
as there are elements.
And just as each element
is different,
so each element's atom has
a different weight -
a unique atomic weight.
Every element has its own signature
atomic weight,
whether it be a solid,
a liquid, or even a gas.
These three balloons are each
filled with a different gas.
Now they are roughly
the same size,
so they should each have
about the same number of atoms in.
Dalton reckoned that different
atoms have different atomic weights.
So these three balloons should
each weigh different amounts.
So this red balloon
is filled with helium gas.
And if I release it,
it floats.
Helium is very light.
This second balloon
is filled with argon gas.
And if I release it,
it sinks slowly.
Argon is heavier than helium.
The third balloon is filled with
krypton gas. And if I let it go,
it falls like a stone.
So Dalton was on the right lines -
different atoms of different
elements have different weights.
Based on this theory,
and working completely alone,
Dalton made one
of the first attempts
to impose some order
on the unruly world of the elements.
This wonderfully mystical set of
symbols is Dalton's line-up
of the elements arranged by weight.
Now there are some elements here
that I don't even recognise,
but he does start
with hydrogen at one.
Then you go down to oxygen at seven,
and all the way down to mercury
at 167.
As it turned out, Dalton didn't
get all of his weights right.
But he had made
a huge theoretical leap
working purely from his mind's eye.
Two hundred years ago,
John Dalton was using
his imagination as a microscope.
But today, we have the technology to
see the contours of individual atoms
with this scanning
tunnelling microscope.
It's not like a normal microscope
because it doesn't use light.
Atoms are less than one
millionth of a millimetre across,
which is smaller than the wavelength
of visible light.
This microscope uses electrons
to scan across the surface
of materials,
picking out individual atoms.
The images it produces are striking.
These are atoms of shining silicon.
These are carbon atoms.
This is what gold atoms look like.
And these are atoms of copper.
Copper is a lustrous metal,
essential for life.
It fuelled the move out of
the Stone Age into the Bronze Age.
Copper nuggets can be found
on the earth's surface,
but it usually needs
to be extracted from ores.
And copper compounds run
in the veins of some animals.
The blood of the octopus is blue,
along with snails, and spiders.
John Dalton's idea
in the early 1800s,
that elements had different
atomic weights,
was dismissed by many scientists.
But one man believed in him -
Swedish chemist
Jons Jakob Berzelius.
Berzelius was obsessed with imposing
some kind of order on the elements.
He was convinced that knowing more
about the weight of each element
was somehow vitally important.
And when he
heard about Dalton's theory,
he came up with an ambitious plan.
It was a gargantuan task.
In fact, it seems almost mad.
This lone Swedish chemist set out
to measure precisely the atomic
weight of every single element,
and this without a shred of proof
that atoms even existed.
But before Berzelius could start,
he was going to have to purify,
dilute, filter
each element incredibly accurately.
And that was far
from straightforward.
At the time,
very little of the crucial
chemical apparatus
needed for work of this precision
had even been invented.
But that wasn't going to stop
a man like Berzelius.
He was on a mission.
So Berzelius set out to
make his own lab equipment.
Ah, Liam. Hi, Jim. Nice to meet you.
Come through to the hotshop.
'Liam Reeves,
a professional glassblower
'at the Royal College of Art will
show me how Berzelius did it.
'Glassblowing is physically
demanding,
'and calls for working at
punishingly high temperatures.
'Berzelius
must have been very dedicated.'
I'm getting the glass out now,
which is at about
1,000 degrees centigrade.
I'm using a wooden block
just to cool and shape the glass.
What is it you're making?
It will be a round-bottomed flask,
which would have been part of the
basic chemistry equipment
that Berzelius would have used. Now
I'm going to introduce some air,
which I'll trap in the pipe
and the heat makes expand.
Wow! How hard would it have been
for Berzelius to learn to do this?
They say it takes 12 years to
kind of...to really master glass.
He was a very skilled glassblower
from the evidence
that I've seen of his work.
What he was making was
high-precision apparatus,
so that must have made it
far more difficult
than your average vase or tumbler.
From the pictures that I've seen,
I've got no idea how he made it.
Really? Yeah. No idea. So I'm just
making the top of the bottle now.
Right, so that's a basic
round-bottomed flask
very much like one
that Berzelius would have made.
Glassblowing isn't something
theoretical physicists like me
normally do.
But I want to find out for myself
just how hard it is to
master this new skill.
OK, just turn a little bit slower.
Come back ever so slightly.
Ah! Well, my arm's burning up.
I'll shield you, actually.
Oh, that's better.
'It's going rather well.'
SNAP!
Oh-h!
Oh, well.
That just goes to show how
difficult this is.
So it does take 12 years to do.
I think you would have
managed it in seven or eight.
There's my flask
dying slowly, melting away.
I mean, it just goes to prove
how incredibly talented
Berzelius was - he wasn't making
something basic like this,
he was making
some really intricate stuff.
'And although he was searching for
elemental order, there was a bonus.'
The great thing, you see,
about Berzelius was that the skills
he learned as a glassblower
led him to an incredible discovery.
In 1824, he discovered
a new element,
because he found that one of the
constituents of glass was silicon.
Silicon is a semi-metallic element...
found within some meteorites.
Closer to home, it's under your feet.
The earth's crust is made
primarily of silicate minerals.
Silicon is its second most
abundant element, after oxygen.
It's mostly found in nature
as sand or quartz.
Its man-made compounds
can be heat resistant,
water resistant and non-stick.
But silicon's ultimate achievement
has to be the silicon chip,
shrinking computers
from room size to palm size.
Silicon was the last of four
elements that Berzelius isolated,
along with thorium,
cerium, and selenium.
He then spent the next decade
of his life
measuring atomic weight after
atomic weight after atomic weight
in an obsessive pursuit of logic
in the face of the seemingly random
chaos of the natural world.
Berzelius laboriously studied
over 2,000 chemical compounds
with staggering dedication.
He weighed, he measured and he
agonised over the tiniest detail
until he'd found out the relative
weights of 45 different elements.
Some of his results
were remarkably accurate.
His weight for chlorine, a gas,
got to within a fifth
of a per cent of what we know today.
But by the time Berzelius
produced his results,
other scientists had started
measuring atomic weights
and come up with completely
different answers.
Now they were pitted
against each other,
perhaps fuelled by an innate
desire to find meaning in disorder.
Berzelius's quest
for order was contagious.
Scientists began looking for
patterns everywhere.
One of these was German chemist
Johann Wolfgang Dobereiner.
He believed that the answer
lay not with atomic weights
but with the elements'
chemical properties and reactions.
'Dr Andrea Sella has studied
Dobereiner's work
'on chemical groups.'
What Dobereiner had really spotted
was that if you considered
all the elements that were known to
that time,
you could often pick out three -
"triads", as he called them,
which had very, very closely
related chemical properties.
And as an example, we have here
the alkali metals.
And I'm going to take the first
and the lightest of them, lithium.
And we have to store these under oil
because they tend to react with air
and moisture. So here goes lithium.
Pop it in.
Oh, look, fizzing away, yeah.
You can see it fizzing.
And the fizzing is hydrogen,
flammable air, being released.
And at the same time,
it's leaving a pink trail.
We've put a bit of indicator
in there, which is telling us
that what's left behind is caustic.
It's actually making
an alkaline solution.
I'm breathing in some caustic soda!
Well, you're getting a little
bit of steam coming off,
and the reaction
is very, very exothermic.
In other words,
the temperature rises a lot,
and the metal has actually melted.
The second metal in this triad
was sodium.
And when we drop the sodium in...
Whoa!
Oh, look at that, flashes of light!
Orange sparks. And those orange
sparks are the same colour
as what you get in streetlights.
Streetlights have sodium in them.
Right.
Well, the third one in the series
is potassium.
The potassium
turns out to be the tiger.
And we may need to stand back.
Look at those flashes. Wow!
And you can see that lilac flame.
And one could really see trends
in these triads.
They're all doing the
same thing, aren't they? Yes.
The fizzing is telling us
that hydrogen is coming off.
We're getting
the alkali being formed.
But the lithium is relatively tame,
the sodium was more excitable,
the potassium starts getting scary.
Dobereiner realised that these
elements must be a family
because they reacted
in a similar way.
Here was the hint of a pattern.
But it only worked on
a few of the elements.
It got scientists no further
than atomic weights had done.
The bigger picture, the universal
order of all the elements,
was still hard to see.
And that wouldn't change until
a breakthrough
by one of greatest minds
in 19th-century science.
In 1848, in the far west of Siberia,
a massive fire destroyed a factory.
The factory manager
faced destitution.
She was a widow, Maria Mendeleeva,
and she made a remarkable sacrifice
for her precociously intelligent son,
14-year-old Dmitri Mendeleev.
Maria was well aware
of her son's intelligence,
and with a steely determination
she set out to get him an education.
So, together with Dmitri, she set
off on a 1,300-mile journey
from Siberia to St Petersburg.
And incredibly, they walked a good
part of that journey.
I'm following in their footsteps
to St Petersburg,
then the capital
of the Russian empire.
After their arduous journey across
the Russian steppes,
mother and son
finally arrived at St Petersburg.
Maria Mendeleeva
had got what she wanted,
but the effort destroyed her.
She died ten weeks later.
The story goes that her
last words to her son were -
"Refrain from illusions and
seek divine and scientific truth."
And young Mendeleev promised to obey.
He studied day and night
to fulfil his mother's dream
and became the most brilliant
chemistry student of his generation.
Chemistry had come a long way since
the Greeks' idea of four elements -
earth, air, fire and water.
But there was still no order
to the 63 elements
that had so far been discovered.
Now the search for a pattern gripped
some of the best minds in science.
But no-one could agree
how to find it.
Mendeleev was still a student
when he attended
the world's first ever international
chemistry conference.
The world's chemists had gathered
to settle the dispute
that was holding back their subject,
the confusion over atomic weights.
Mendeleev watched as Sicilian
chemist Stanislao Cannizzaro
stole the show.
Cannizzaro was still convinced
that atomic weights held the
key to the elements,
and he'd struck on
a wonderful innovation,
a reliable new way
of calculating them.
He knew that equal volumes of gases
contain equal numbers of molecules.
So instead of working with
liquids and solids,
his breakthrough was to use
the densities of gases and vapours
to measure the atomic weights
of single atoms.
Cannizzaro gave a talk in which he
presented striking new evidence
that won over
the assembled chemists.
So whereas Berzelius's work
had failed to convince anyone,
Cannizzaro's new method
set an agreed standard.
Finally, chemists had a way of
measuring atomic weights accurately.
It was the moment everybody
had been waiting for.
Surely with precise atomic weights
they would now be able to unravel
the mystery of the elements?
One chemist wrote, "It was as
though the scales fell from my eyes
"and doubt was replaced
by peaceful clarity."
There was a real buzz in the air.
Finally, it seemed that
the order of the elements
may have been within
science's grasp.
Mendeleev was electrified.
But chemists soon found that even
arranged in order of atomic weight,
the elements appeared unsystematic.
They were still
missing something vital.
Then, in 1863,
a solitary English chemist
named John Newlands
made an unusual discovery.
Newlands noticed that when the
elements are arranged by weight,
something very strange happened.
Imagine each element is like
a key on the piano,
arranged by their atomic weight.
Then this will be carbon,
followed by nitrogen,
oxygen, fluorine, sodium,
magnesium, aluminium
and finally silicon.
'Thinking of the elements
like a musical scale,
'Newlands reckoned that every
octave, every eight notes,
'certain properties
seemed to repeat, to harmonise.'
He called it a "law of octaves".
It was the first real attempt
to find a law of nature
that pulled all the known
elements together.
Newlands proudly presented his idea
to the great and the good
of the Chemical Society in 1866.
It was his big moment.
But his music analogy
didn't seem to strike a chord.
They completely
failed to see his point.
The assembled chemists said
Newlands' idea was ridiculous,
that he might as well have arranged
the elements alphabetically
for all the insight his theory gave.
Maybe, they even suggested
with biting sarcasm,
that Newlands could get his
elements to play them a little tune.
It must have been a shattering
blow for Newlands.
But was John Newlands
really onto something
with his curious law of octaves?
It's such a bizarre concept
that every eighth element
will behave in a similar way.
It's not surprising that people
thought Newlands' idea was mad.
Here are eight elements
in order of their atomic weight,
and I'm going to explore their
properties by smelling them.
The first element is chlorine.
It's a yellowy-green gas
that's highly toxic.
If I have a sniff...
Yep, distinctive smell of bleach.
The second one is potassium.
But no odour to it at all.
'And as I smell my way through
the next five elements,
'calcium, gallium, germanium,
arsenic -
'not poisonous to smell
in its pure form -
'and selenium, there's no scent.'
Finally number eight, bromine.
I already see it's a gas,
like chlorine, a reddish gas,
highly toxic.
I'm going to be very careful,
because I don't recommend
you try this at home.
Smells very much like chlorine,
only a lot worse, a lot stronger.
And so Newlands' law of octaves
seems to work here,
because the eighth element, bromine,
is similar in properties
to the first one, chlorine.
'Today we know Newlands' law of
octaves as the law of periodicity.
' But at the time,
the establishment scoffed.
' And Newlands
never got over the slight.
'The way was left clear
for Dmitri Mendeleev,
'who was thinking along
the same lines.'
I'm on my way to
St Petersburg University
to meet a man who will hopefully show
me where Mendeleev actually worked.
Hello, Professor Babaev.
Hi, I'm Jim. Good to meet you.
It's very exciting.
OK, well, the museum...
Right, well, lead on.
'Professor Eugene Babaev is
the leading expert on Mendeleev,
'having studied his work many years.
'He's going take me
inside Mendeleev's apartment,
'preserved just as it was
during the last years of his life.
'This is a great honour.
'Normally, nobody is allowed
inside Mendeleev's study.'
So this is quite a privilege,
to be able to come in here.
Look at this. Fantastic.
'Mendeleev shut himself away in this
room, brooding over the elements.
'This would become the birthplace
'of one of science's greatest
achievements, the periodic table.'
And I love this photo of him.
This is the photo of 1869,
just the year when... Ah!
So that's what he looked like when
he came up with the periodic table.
And these are all his original books.
These are his books, written by him.
Oh, I see.
When I say "his books",
not owned by him.
These are the books that he wrote.
Thousands of volumes.
That's impressive.
OK, and if you look at his library,
you will be surprised,
because maybe 10% of the books are
devoted to chemistry and physics
but everything else is economics,
technics, er...
geography, whatever.
He was a polymath.
Yes, and his second wife
was a painter,
and one portrait
here in profile is just by her work.
'Mendeleev had such a breadth
of intellectual curiosity
'he became known as the Russian
Leonardo da Vinci.'
These are the clocks which stopped
at the moment of his death in 1907.
1907, at twenty past six. Yeah.
'It seems as if time has stood still
in this room
'for more than a century.
'And now that I've seen
the inner sanctum
'where Mendeleev puzzled over the
elements, I want to know
'exactly how he pieced together
his masterwork, the periodic table.
'By 1869, Mendeleev had
been trying to find a pattern
'to the elements for a decade.
'Whatever order he and the world's
chemists tried to impose,
'there were still elements
that wouldn't fit.
'A universal theory
seemed out of reach.
'But now Mendeleev hit on a new idea.
'He made up a pack of cards
and wrote an element
'and its atomic weight
on each one.'
Strange though this might sound,
so began the most memorable card
game in the history of science.
He called it chemical solitaire
and began laying out cards just
to see where there was a pattern,
whether it all fitted together.
Now, previously, chemists had grouped
the elements in one of two ways,
either by their properties,
like those that react very strongly
with water,
or by grouping them
by their atomic weight,
which is what
Berzelius and Cannizzaro had done.
Mendeleev's great genius was to
combine those two methods together.
'The odds were stacked against him.
'Little more than half the elements
we now know about
'had been discovered,
' so he was playing with an incomplete
deck of cards.'
He stayed up for three days
and three nights without any sleep,
just thinking solidly
about the problem.
Then, on the 17th of February,
with a snowstorm raging outside,
he decided to stay at home.
He was exhausted,
and he finally he dozed off.
' The story goes he had
an extraordinary dream.
'He saw almost all
of the 63 known elements
'arrayed in a grand table
which related them together.'
It was an incredible breakthrough.
I can imagine Mendeleev feeling like
so many other scientific pioneers.
It's that determination, even
desperation, to crack a puzzle,
and then that
eureka moment of revelation.
Mendeleev had revealed a deep truth
about the nature of our world,
that there is a numerical pattern
underlying the structure of matter.
This is the periodic table
as we know it today,
and it's rooted
in Mendeleev's discovery.
It decodes and makes sense of the
building blocks of the whole world.
Now, although it's so familiar to us,
it's on the wall of every chemistry
lab in every school in the world,
if you really look at it,
it's actually awe inspiring.
What's so remarkable is that it
reveals the relationships
between each and every element
in order.
Mendeleev had brilliantly
combined elements' atomic weights
and properties
into one universal understanding
of all the elements.
Reading it across,
the atomic weights increase step
by step with every element.
But then,
looking at it vertically,
the elements are grouped together
in families of similar properties.
So over on this side are the alkali
metals, from lithium to caesium.
And then over on the far side
are the halogens,
like poisonous chlorine, bromine and
iodine, all very highly reactive.
And alongside them at the top are
the elements important for life -
carbon, nitrogen, oxygen,
all non-metals.
But in the middle, a vast swathe,
are all the metals,
and there are four times
as many metals as non-metals.
Everything is ordered.
It's a chemical landscape
and a perfect map of the geography
of the elements.
'Intriguingly, the periodic table
didn't always look like this.
'Professor Babaev is keen
to show me a copy
'of Mendeleev's very
first manuscript.'
So, this is the first draft of
Mendeleev's periodic table.
You can see the date, 17th February
1869. And it's in his handwriting.
I can see the crossings out, you
can feel his thought processes.
Some familiar elements here.
I see hydrogen, the lightest
element, all the way to lead.
Yeah, yeah. Now you can see some
familiar groups,
like alkali metals, halogens.
It's got lithium, sodium, potassium.
It's not like the periodic table
that I would be familiar with,
it's the other way round.
It took maybe two years
for Mendeleev to bring it
to modern form.
But it's remarkable
that this is the foundations
of the modern periodic table.
It started here.
'Mendeleev's first draft
wasn't perfect.
'To make his table work,
he had to do something astonishing.
'He had to leave spaces for
elements that were still unknown.'
This is a copy of the first published
draft of the periodic table,
and these question marks
are where Mendeleev left gaps.
You see, he was so confident
about his model
that he wouldn't fudge the results.
So where the model didn't work,
he left gaps for elements
that had yet to be discovered.
So, for instance,
this question mark here
he predicted was a metal slightly
heavier than its neighbour calcium.
And here two more metals.
One he predicted would be dark grey
in colour,
and the other would have
a low melting point.
Mendeleev had the audacity to believe
that he would, in time,
be proved right.
It's as if Mendeleev
was a chemical prophet,
foretelling the future
in a visionary interpretation
of the laws of matter.
But before he could claim the glory,
his gaps needed explaining.
And a new way of detecting elements
was invented in 1859.
That was thanks to
Gustav Kirchhoff and his colleague,
the man who made the Bunsen burner.
Robert Bunsen was
a wonderfully intrepid experimenter.
How's this for dedication?
He lost his right eye
in an explosion in his lab.
Now, he knew that when different
elements burned in the flame
of his Bunsen burner,
wonderful colours were revealed.
This one is copper.
This one contains strontium.
And this one is potassium.
Bunsen wondered whether
every element
might have a unique
colour signature,
and so he and Kirchhoff set to work.
Kirchhoff knew that when white light
is shone through a prism
it gets split up into
all its spectral colours...
..all the colours of the rainbow,
from red through yellow
to blue and violet.
And he came up with this.
It's called a spectroscope.
It has a prism in the middle
with two telescopes on either side.
Bunsen and Kirchhoff
then worked together
to analyse different materials
using their new piece of kit.
So they took a compound
containing sodium.
And if I heat it up
in the Bunsen burner,
the light from the sodium
passes through the first telescope
and gets split up by the prism
into its spectral lines.
They then pass through the second
telescope. And if I have a look.
Yep, I can see
the two orange lines
which are the
unique spectrum of sodium.
No other element
would give that pattern.
Using this technique, they actually
discovered two new elements,
silvery-gold caesium,
and rubidium,
so named because of the
ruby-red colour of its spectrum.
It was this same technique that was
used to test
whether Mendeleev's
prediction of gaps was right.
He'd described in meticulous detail
an unknown element that followed
aluminium in his periodic table.
He predicted it would be a silvery
metal with atomic weight 68.
Then, in 1875, a French chemist
used a spectroscope
to identify just such an element -
gallium.
Gallium is a beautiful silvery-white
metal, and it's relatively soft.
Although Mendeleev predicted
its existence,
it was actually found
by Parisian chemist
Paul Emile Lecoq de Boisbaudran.
Gallium has a very low melting point.
And with a boiling point
of 2,204 degrees centigrade,
it's liquid over a wider range of
temperatures
than any other known substance.
Gallium is used to
make semiconductors.
It's found
in light-emitting diodes, LEDs.
One of gallium's compounds was
shown to be effective
in attacking drug-resistant
strains of malaria.
But even though Mendeleev had left
gaps for gallium and other elements,
his table was not complete.
There was one group
that eluded him completely,
an entirely new family of elements.
The story of their discovery
began with an other-worldly search
for an extraterrestrial element.
In August 1868, a total eclipse
of the sun in India was the moment
that French astronomer Pierre
Janssen had been waiting for.
He knew that it was possible to use
a spectroscope
to identify some
elements in the light of the sun.
But the intensity of sunlight meant
that many elements were hidden.
Janssen hoped to see more
during a total eclipse,
when the sun was less blinding.
As Janssen studied the eclipse,
he discovered a colour signature
never seen before.
He was faced with an unknown element.
The same spectral line was confirmed
by another astronomer,
Norman Lockyer.
He named it helium,
after the Greek sun god,
because he thought that
it could only exist on the sun.
Enter Scottish chemist
William Ramsay,
who linked extraterrestrial
helium to Earth.
Ramsay experimented with a
radioactive rock called cleveite.
By dissolving the rock in acid,
he collected a gas
with an atomic weight of 4
and the same spectral signature
that Lockyer had seen, helium.
Helium is the second most abundant
element in the universe,
after hydrogen.
It was one of the elements
produced just after the Big Bang.
Liquid helium is
used to cool superconducting magnets
for MRI scanners.
Deep-sea divers rely on helium
to counter the narcotic effects
on the brain
of increased nitrogen absorption.
And it was a vital ingredient in the
space race,
used to cool hydrogen
and oxygen for rocket engines.
Before he discovered helium on Earth,
William Ramsay had already separated
a new gas from the air, argon,
with an atomic weight of 40.
Now Ramsay faced a puzzle.
He realised that the new elements
didn't fit the periodic table
and suggested
there must be a missing group,
so his search began.
He found three more gases, which
he named neon, Greek for "new",
krypton, meaning "hidden",
and xenon, "stranger".
The group became known as
the noble gases
because they were unreactive
and seemed so aloof.
This family of gases completed
the rows on the periodic table.
Now, Mendeleev may not have
known about these elusive elements,
but he'd established the unshakeable
idea of elemental relationships.
And so he made sure
that there was a place on his table
for every new element,
no matter when it was discovered.
The periodic table is a
classic example
of the scientific method at work.
From a mass of data,
Mendeleev found a pattern.
It led him to make predictions
that could be tested
by future experiments,
pointing the way for
20th-century scientists
to prove him and his theory right.
By the time he died
at the age of 72,
he was a hero in Russia and
a superhero in the world of science.
His periodic table
was immortalised in stone
here in the centre
of St Petersburg,
and he eventually had an element
named after him, mendelevium,
as well as a crater,
the Mendeleev Crater,
on the dark side of the moon...
..fitting tributes to a man who
came from the Siberian wastelands
to become the ultimate
cartographer of the elements.
The periodic table had
finally created order out of chaos.
But it tells us nothing about
WHY our world is as it is,
why some elements are energetic,
others are slow, some inert,
others volatile.
It would be another 40 years
before an entirely different branch
of science came up with an answer.
In 1909, Ernest Rutherford looked
inside the atom for the first time.
Rutherford proposed that
the structure of the atom
was like a miniature solar system,
an overwhelmingly empty space
with a few tiny electrons
orbiting randomly around a dense,
positively-charged nucleus.
But it wasn't until Niels Bohr
came along, one-time goalkeeper
for the Danish football squad and
future Nobel prize-winning physicist
that things really kicked off.
He suggested that the electrons
orbited around the nucleus
in fixed shells.
And it was his idea that was to lead
to the discovery that these shells
could only accommodate
a set number of electrons.
Imagine this football pitch is an
atom, a single atom of an element.
This is the nucleus.
If this nucleus were to scale,
my nearest orbiting electrons
would be beyond the stands,
so I've scaled it down.
Here, on the shell
nearest to the nucleus,
there can be just two electrons,
then it's full.
Here in the second shell,
there can be eight electrons,
then it's fully occupied, too.
The third shell is happy with
18 electrons. And so it goes on.
Outer shells can accommodate an
increasing number of electrons.
So electrons sit in discrete shells,
never in-between the shells.
Bohr's theory would explain
WHY elements behave as they do.
It turns out that it's all to
do with the number of electrons
in the outermost shell.
So, for example, Bohr's model showed
that sodium has eleven electrons -
two here, eight here
and just one in its outer shell.
And fluorine has nine - two here
and seven in its outer shell.
To be completely stable,
atoms like to have a full
outer shell of electrons.
So a sodium atom would
like to lose an electron,
to have a completely
full outer shell,
whereas a fluorine atom has a gap
in its outer shell,
so by gaining an electron
it can complete it.
In this way, a sodium atom and a
fluorine atom can stick together
by exchanging an electron,
making sodium fluoride.
Bohr's work and that
of many other scientists
in the early part
of the 20th century
led to an explanation of every
element and every compound,
why some elements react together
to make compounds
and why others didn't,
why the elements had the
properties that they did,
and this in turn
explained why the periodic table
had the shape that it did.
Mendeleev had managed to reveal
a universal pattern
without understanding
why it should be so.
To find the answer, physicists had
to delve into a subatomic world
that Mendeleev
didn't even know existed.
This work was nothing
short of a triumph.
Even Albert Einstein was impressed.
He wrote, "This is the highest
form of musicality
"in the sphere of thought."
But there was still one
fundamental question left to answer.
How many elements were there?
Could there be an infinite number
between hydrogen,
with the lightest atomic weight,
and uranium,
the heaviest known element?
In the early 20th century,
a brilliant young English physicist,
Henry Moseley,
was determined to find out.
He speculated that the secret
lay within the nucleus
at the heart of each atom.
Moseley developed a unique way
of studying atoms.
Scientists still use
a similar technique today,
although this X-ray spectrometer
looks a bit different to the sort
of kit Moseley that would have used.
One of the elements that he studied
was copper,
and there's a small piece
of copper inside here.
Now, behind it
is a radioactive source
that fires high-energy radiation
at the copper atoms.
Moseley knew that the nucleus
of the atom
contains positively-charged
particles we call protons.
He also knew that surrounding
the nucleus
are negatively-charged electrons.
Now, the radiation being fired at
the copper
is knocking some of the electrons
from the atoms,
and this had the effect
of making the atoms give off
a burst of energy, an X-ray.
And Moseley
found a way of measuring it.
He made a startling discovery.
He found that copper atoms always
give off the same amount of energy.
On this graph,
it's shown by this spike.
And no matter how many times
I repeat this experiment,
I will always get
the spike in the same position.
It's unique to copper.
Mosley also
experimented with other elements.
And inside this sample
there are several others.
So if I move this on
to the next one,
which is rubidium,
and run this again,
I get another spike
in a different position.
And if I move it on again to the
next one, which is molybdenum,
I see a third spike
in a new position.
Every element has its own
energy signature.
But his stroke of brilliance
was to realise
that this is related
to the number of protons.
He was the first person to measure
the number of protons
in the nucleus of an element,
the atomic number.
Atomic numbers are whole numbers,
so, unlike atomic weights,
there can't be
any awkward fractions.
For example, chlorine
has an atomic weight
that comes
in an inconvenient half, 35.5,
but a whole atomic number, 17.
So Moseley realised
that it's the atomic number,
not the atomic weight,
that determines the number
and the order of the elements.
And this is where it gets
really clever.
Because the atomic number
goes up in whole numbers,
there could be no extra elements
between element number one,
hydrogen,
and number 92, uranium.
92 elements is all there could be.
There's just no more room.
So Henry Moseley did the groundwork
that enables us to say
with absolute confidence
that there are 92 elements,
from hydrogen
all the way to uranium.
Mosley was just 26 when he
completed his research,
but his genius
was lost tragically early.
At the outbreak of World War I,
he volunteered to fight,
even though, as a scientist,
he could have avoided joining up.
He was killed in action aged just 27,
shot through the head by a sniper.
A colleague wrote, "In view of what
he might still have accomplished,
"his death might well have been
the single most costly death
"of the war to mankind."
The periodic table is a wonderful
fusion of chemistry and physics.
Mendeleev and the chemists worked
from the outside,
with the chemical properties
of each element,
and the physicists
worked from the inside,
with the invisible world
of the atom.
And yet
both had arrived at the same point.
The ordered design of the natural
world had finally been explained
in a pattern of pure,
intellectual beauty.
So an era that had begun
with scientists groping
towards an understanding
of the basic building blocks
of our world
had ended with
that world entirely classified
and made clear for all to see.
And we never looked back.
Next time, I'll follow
in the footsteps of the chemists
who laboured
to control the elements
and combine them
into the billions of compounds
that make up the modern world...
..I'll discover how
modern-day alchemists
are attempting to push
at the wildest outposts
of the periodic table
to create brand-new elements,
and I'll find out how the power
of the elements was harnessed
to release
almost unimaginable forces.
Subtitles by Red Bee Media Ltd
chemist had an extraordinary vision.
He'd been struggling with
a mystery
that had perplexed
scientists for generations.
And for the very first time, he'd
glimpsed nature's building blocks,
the elements,
arranged in their natural order.
His name was Dmitri Mendeleev,
and he was on the brink of cracking
the secret code of the Cosmos,
what was to become one of man's
most beautiful creations,
the Periodic Table of Elements.
This is the story of those elements,
the building blocks that make up
the universe...
..the remarkable tale
of their discovery,
and how they fit together, reveals
how the modern world was made.
'My name's Jim Al-Khalili.
And ever since I started studying
the mysteries of matter,
'I've been fascinated by
chemistry's explosive history...'
Ho-ho! Brilliant!
'..I've discovered some
exciting elements...'
That's fantastic!
'..and I've seen how chemistry
was forged
'in the furnaces of the alchemists.
'Now I'm going to continue
my journey.
'I'll take up the quest
of the chemical pioneers...'
Well, my arm's burning up.
'...as they struggled to make sense
of elemental chaos
'and conquer
our fundamental fear of disorder.
'Could there be a grand plan
underlying the elements?
'I'll take part in some
volatile experiments...'
Now we're going to drop
in the potassium.
Wow, look at that! Wahey!
'..and witness some
fiery reactions.'
And I'll find out how the hidden
order of the natural world
was revealed in all its glory -
the order of the elements.
As a nuclear physicist,
I've spent a lifetime studying
the sub-atomic world,
the basic building blocks
of matter.
But to do that, I need to understand
the ingredients of OUR world...
..the elements.
Our planet was created
from just 92 elements.
The ground we walk on, the air that
we breathe, the stars we gaze at,
even us.
Our bodies are
entirely made of elements.
We now know the name and number
of every naturally-occurring
element in existence.
But 200 years ago,
those elements were only just
beginning to give up their secrets.
At the beginning
of the 19th century,
only 55 had been discovered,
from liquid mercury
to dazzling magnesium...
..and volatile iodine.
Scientists had no idea how many more
they might find,
or whether there
could be an infinite number.
But the big question was,
how did they fit together?
Were they random stars,
or was the elemental world born of
order and logic?
Solving the puzzle would prove
to be a daunting challenge.
And the first glimmerings of an
answer came from an unlikely source.
John Dalton
was an intelligent, modest man,
and he had one
very British passion - the weather.
He was born here
in the Lake District in 1766.
He was so clever, that
as a young boy, just 12 years old,
he was already teaching other kids
at a school that he set up.
Walking home, he loved watching
the weather systems
sweeping across the fells.
He was so obsessed that he kept
a meteorological diary for 57 years,
and every single day,
come rain or shine,
he entered his precise
observations - 200,000 of them.
Dalton was a quiet,
retiring man with modest habits.
He was a lifelong bachelor, with not
much in the way of a social life.
His only recreation
was a game of bowls once a week,
every Thursday afternoon.
He was certainly
a creature of habit,
and he might sound a bit dull.
But actually, Dalton was
an avid reader and a deep thinker.
Underneath his mild-mannered
exterior,
his head was teeming
with radical ideas.
Now scientists had recently
discovered something very important
about the way elements combine
to form compounds.
When they do so, they always combine
in the same proportions.
Dalton would have known that
table salt, sodium chloride,
is always made up of one part
sodium and one part chlorine.
So it doesn't matter whether the
salt comes from Salt Lake City
or Siberia, it's always in the same
proportion by weight, every time.
Dalton reckoned for this to happen,
each element had to be made up
of its own unique building blocks,
what he called
"ultimate particles", atoms.
It was a blinding illumination,
completely left field.
Everything, he suggested,
the entire universe,
was made up of infinitesimally
small particles.
The Greeks had hit on the idea
of the atom 2,000 years earlier,
but abandoned it.
Now, Dalton took up the baton
with his own theory of matter.
What Dalton was describing
was revolutionary.
He had struck on the foundations
of atomic theory,
foreshadowing research that wouldn't
be proved until a century later.
He proposed that there are as many
kinds of atoms
as there are elements.
And just as each element
is different,
so each element's atom has
a different weight -
a unique atomic weight.
Every element has its own signature
atomic weight,
whether it be a solid,
a liquid, or even a gas.
These three balloons are each
filled with a different gas.
Now they are roughly
the same size,
so they should each have
about the same number of atoms in.
Dalton reckoned that different
atoms have different atomic weights.
So these three balloons should
each weigh different amounts.
So this red balloon
is filled with helium gas.
And if I release it,
it floats.
Helium is very light.
This second balloon
is filled with argon gas.
And if I release it,
it sinks slowly.
Argon is heavier than helium.
The third balloon is filled with
krypton gas. And if I let it go,
it falls like a stone.
So Dalton was on the right lines -
different atoms of different
elements have different weights.
Based on this theory,
and working completely alone,
Dalton made one
of the first attempts
to impose some order
on the unruly world of the elements.
This wonderfully mystical set of
symbols is Dalton's line-up
of the elements arranged by weight.
Now there are some elements here
that I don't even recognise,
but he does start
with hydrogen at one.
Then you go down to oxygen at seven,
and all the way down to mercury
at 167.
As it turned out, Dalton didn't
get all of his weights right.
But he had made
a huge theoretical leap
working purely from his mind's eye.
Two hundred years ago,
John Dalton was using
his imagination as a microscope.
But today, we have the technology to
see the contours of individual atoms
with this scanning
tunnelling microscope.
It's not like a normal microscope
because it doesn't use light.
Atoms are less than one
millionth of a millimetre across,
which is smaller than the wavelength
of visible light.
This microscope uses electrons
to scan across the surface
of materials,
picking out individual atoms.
The images it produces are striking.
These are atoms of shining silicon.
These are carbon atoms.
This is what gold atoms look like.
And these are atoms of copper.
Copper is a lustrous metal,
essential for life.
It fuelled the move out of
the Stone Age into the Bronze Age.
Copper nuggets can be found
on the earth's surface,
but it usually needs
to be extracted from ores.
And copper compounds run
in the veins of some animals.
The blood of the octopus is blue,
along with snails, and spiders.
John Dalton's idea
in the early 1800s,
that elements had different
atomic weights,
was dismissed by many scientists.
But one man believed in him -
Swedish chemist
Jons Jakob Berzelius.
Berzelius was obsessed with imposing
some kind of order on the elements.
He was convinced that knowing more
about the weight of each element
was somehow vitally important.
And when he
heard about Dalton's theory,
he came up with an ambitious plan.
It was a gargantuan task.
In fact, it seems almost mad.
This lone Swedish chemist set out
to measure precisely the atomic
weight of every single element,
and this without a shred of proof
that atoms even existed.
But before Berzelius could start,
he was going to have to purify,
dilute, filter
each element incredibly accurately.
And that was far
from straightforward.
At the time,
very little of the crucial
chemical apparatus
needed for work of this precision
had even been invented.
But that wasn't going to stop
a man like Berzelius.
He was on a mission.
So Berzelius set out to
make his own lab equipment.
Ah, Liam. Hi, Jim. Nice to meet you.
Come through to the hotshop.
'Liam Reeves,
a professional glassblower
'at the Royal College of Art will
show me how Berzelius did it.
'Glassblowing is physically
demanding,
'and calls for working at
punishingly high temperatures.
'Berzelius
must have been very dedicated.'
I'm getting the glass out now,
which is at about
1,000 degrees centigrade.
I'm using a wooden block
just to cool and shape the glass.
What is it you're making?
It will be a round-bottomed flask,
which would have been part of the
basic chemistry equipment
that Berzelius would have used. Now
I'm going to introduce some air,
which I'll trap in the pipe
and the heat makes expand.
Wow! How hard would it have been
for Berzelius to learn to do this?
They say it takes 12 years to
kind of...to really master glass.
He was a very skilled glassblower
from the evidence
that I've seen of his work.
What he was making was
high-precision apparatus,
so that must have made it
far more difficult
than your average vase or tumbler.
From the pictures that I've seen,
I've got no idea how he made it.
Really? Yeah. No idea. So I'm just
making the top of the bottle now.
Right, so that's a basic
round-bottomed flask
very much like one
that Berzelius would have made.
Glassblowing isn't something
theoretical physicists like me
normally do.
But I want to find out for myself
just how hard it is to
master this new skill.
OK, just turn a little bit slower.
Come back ever so slightly.
Ah! Well, my arm's burning up.
I'll shield you, actually.
Oh, that's better.
'It's going rather well.'
SNAP!
Oh-h!
Oh, well.
That just goes to show how
difficult this is.
So it does take 12 years to do.
I think you would have
managed it in seven or eight.
There's my flask
dying slowly, melting away.
I mean, it just goes to prove
how incredibly talented
Berzelius was - he wasn't making
something basic like this,
he was making
some really intricate stuff.
'And although he was searching for
elemental order, there was a bonus.'
The great thing, you see,
about Berzelius was that the skills
he learned as a glassblower
led him to an incredible discovery.
In 1824, he discovered
a new element,
because he found that one of the
constituents of glass was silicon.
Silicon is a semi-metallic element...
found within some meteorites.
Closer to home, it's under your feet.
The earth's crust is made
primarily of silicate minerals.
Silicon is its second most
abundant element, after oxygen.
It's mostly found in nature
as sand or quartz.
Its man-made compounds
can be heat resistant,
water resistant and non-stick.
But silicon's ultimate achievement
has to be the silicon chip,
shrinking computers
from room size to palm size.
Silicon was the last of four
elements that Berzelius isolated,
along with thorium,
cerium, and selenium.
He then spent the next decade
of his life
measuring atomic weight after
atomic weight after atomic weight
in an obsessive pursuit of logic
in the face of the seemingly random
chaos of the natural world.
Berzelius laboriously studied
over 2,000 chemical compounds
with staggering dedication.
He weighed, he measured and he
agonised over the tiniest detail
until he'd found out the relative
weights of 45 different elements.
Some of his results
were remarkably accurate.
His weight for chlorine, a gas,
got to within a fifth
of a per cent of what we know today.
But by the time Berzelius
produced his results,
other scientists had started
measuring atomic weights
and come up with completely
different answers.
Now they were pitted
against each other,
perhaps fuelled by an innate
desire to find meaning in disorder.
Berzelius's quest
for order was contagious.
Scientists began looking for
patterns everywhere.
One of these was German chemist
Johann Wolfgang Dobereiner.
He believed that the answer
lay not with atomic weights
but with the elements'
chemical properties and reactions.
'Dr Andrea Sella has studied
Dobereiner's work
'on chemical groups.'
What Dobereiner had really spotted
was that if you considered
all the elements that were known to
that time,
you could often pick out three -
"triads", as he called them,
which had very, very closely
related chemical properties.
And as an example, we have here
the alkali metals.
And I'm going to take the first
and the lightest of them, lithium.
And we have to store these under oil
because they tend to react with air
and moisture. So here goes lithium.
Pop it in.
Oh, look, fizzing away, yeah.
You can see it fizzing.
And the fizzing is hydrogen,
flammable air, being released.
And at the same time,
it's leaving a pink trail.
We've put a bit of indicator
in there, which is telling us
that what's left behind is caustic.
It's actually making
an alkaline solution.
I'm breathing in some caustic soda!
Well, you're getting a little
bit of steam coming off,
and the reaction
is very, very exothermic.
In other words,
the temperature rises a lot,
and the metal has actually melted.
The second metal in this triad
was sodium.
And when we drop the sodium in...
Whoa!
Oh, look at that, flashes of light!
Orange sparks. And those orange
sparks are the same colour
as what you get in streetlights.
Streetlights have sodium in them.
Right.
Well, the third one in the series
is potassium.
The potassium
turns out to be the tiger.
And we may need to stand back.
Look at those flashes. Wow!
And you can see that lilac flame.
And one could really see trends
in these triads.
They're all doing the
same thing, aren't they? Yes.
The fizzing is telling us
that hydrogen is coming off.
We're getting
the alkali being formed.
But the lithium is relatively tame,
the sodium was more excitable,
the potassium starts getting scary.
Dobereiner realised that these
elements must be a family
because they reacted
in a similar way.
Here was the hint of a pattern.
But it only worked on
a few of the elements.
It got scientists no further
than atomic weights had done.
The bigger picture, the universal
order of all the elements,
was still hard to see.
And that wouldn't change until
a breakthrough
by one of greatest minds
in 19th-century science.
In 1848, in the far west of Siberia,
a massive fire destroyed a factory.
The factory manager
faced destitution.
She was a widow, Maria Mendeleeva,
and she made a remarkable sacrifice
for her precociously intelligent son,
14-year-old Dmitri Mendeleev.
Maria was well aware
of her son's intelligence,
and with a steely determination
she set out to get him an education.
So, together with Dmitri, she set
off on a 1,300-mile journey
from Siberia to St Petersburg.
And incredibly, they walked a good
part of that journey.
I'm following in their footsteps
to St Petersburg,
then the capital
of the Russian empire.
After their arduous journey across
the Russian steppes,
mother and son
finally arrived at St Petersburg.
Maria Mendeleeva
had got what she wanted,
but the effort destroyed her.
She died ten weeks later.
The story goes that her
last words to her son were -
"Refrain from illusions and
seek divine and scientific truth."
And young Mendeleev promised to obey.
He studied day and night
to fulfil his mother's dream
and became the most brilliant
chemistry student of his generation.
Chemistry had come a long way since
the Greeks' idea of four elements -
earth, air, fire and water.
But there was still no order
to the 63 elements
that had so far been discovered.
Now the search for a pattern gripped
some of the best minds in science.
But no-one could agree
how to find it.
Mendeleev was still a student
when he attended
the world's first ever international
chemistry conference.
The world's chemists had gathered
to settle the dispute
that was holding back their subject,
the confusion over atomic weights.
Mendeleev watched as Sicilian
chemist Stanislao Cannizzaro
stole the show.
Cannizzaro was still convinced
that atomic weights held the
key to the elements,
and he'd struck on
a wonderful innovation,
a reliable new way
of calculating them.
He knew that equal volumes of gases
contain equal numbers of molecules.
So instead of working with
liquids and solids,
his breakthrough was to use
the densities of gases and vapours
to measure the atomic weights
of single atoms.
Cannizzaro gave a talk in which he
presented striking new evidence
that won over
the assembled chemists.
So whereas Berzelius's work
had failed to convince anyone,
Cannizzaro's new method
set an agreed standard.
Finally, chemists had a way of
measuring atomic weights accurately.
It was the moment everybody
had been waiting for.
Surely with precise atomic weights
they would now be able to unravel
the mystery of the elements?
One chemist wrote, "It was as
though the scales fell from my eyes
"and doubt was replaced
by peaceful clarity."
There was a real buzz in the air.
Finally, it seemed that
the order of the elements
may have been within
science's grasp.
Mendeleev was electrified.
But chemists soon found that even
arranged in order of atomic weight,
the elements appeared unsystematic.
They were still
missing something vital.
Then, in 1863,
a solitary English chemist
named John Newlands
made an unusual discovery.
Newlands noticed that when the
elements are arranged by weight,
something very strange happened.
Imagine each element is like
a key on the piano,
arranged by their atomic weight.
Then this will be carbon,
followed by nitrogen,
oxygen, fluorine, sodium,
magnesium, aluminium
and finally silicon.
'Thinking of the elements
like a musical scale,
'Newlands reckoned that every
octave, every eight notes,
'certain properties
seemed to repeat, to harmonise.'
He called it a "law of octaves".
It was the first real attempt
to find a law of nature
that pulled all the known
elements together.
Newlands proudly presented his idea
to the great and the good
of the Chemical Society in 1866.
It was his big moment.
But his music analogy
didn't seem to strike a chord.
They completely
failed to see his point.
The assembled chemists said
Newlands' idea was ridiculous,
that he might as well have arranged
the elements alphabetically
for all the insight his theory gave.
Maybe, they even suggested
with biting sarcasm,
that Newlands could get his
elements to play them a little tune.
It must have been a shattering
blow for Newlands.
But was John Newlands
really onto something
with his curious law of octaves?
It's such a bizarre concept
that every eighth element
will behave in a similar way.
It's not surprising that people
thought Newlands' idea was mad.
Here are eight elements
in order of their atomic weight,
and I'm going to explore their
properties by smelling them.
The first element is chlorine.
It's a yellowy-green gas
that's highly toxic.
If I have a sniff...
Yep, distinctive smell of bleach.
The second one is potassium.
But no odour to it at all.
'And as I smell my way through
the next five elements,
'calcium, gallium, germanium,
arsenic -
'not poisonous to smell
in its pure form -
'and selenium, there's no scent.'
Finally number eight, bromine.
I already see it's a gas,
like chlorine, a reddish gas,
highly toxic.
I'm going to be very careful,
because I don't recommend
you try this at home.
Smells very much like chlorine,
only a lot worse, a lot stronger.
And so Newlands' law of octaves
seems to work here,
because the eighth element, bromine,
is similar in properties
to the first one, chlorine.
'Today we know Newlands' law of
octaves as the law of periodicity.
' But at the time,
the establishment scoffed.
' And Newlands
never got over the slight.
'The way was left clear
for Dmitri Mendeleev,
'who was thinking along
the same lines.'
I'm on my way to
St Petersburg University
to meet a man who will hopefully show
me where Mendeleev actually worked.
Hello, Professor Babaev.
Hi, I'm Jim. Good to meet you.
It's very exciting.
OK, well, the museum...
Right, well, lead on.
'Professor Eugene Babaev is
the leading expert on Mendeleev,
'having studied his work many years.
'He's going take me
inside Mendeleev's apartment,
'preserved just as it was
during the last years of his life.
'This is a great honour.
'Normally, nobody is allowed
inside Mendeleev's study.'
So this is quite a privilege,
to be able to come in here.
Look at this. Fantastic.
'Mendeleev shut himself away in this
room, brooding over the elements.
'This would become the birthplace
'of one of science's greatest
achievements, the periodic table.'
And I love this photo of him.
This is the photo of 1869,
just the year when... Ah!
So that's what he looked like when
he came up with the periodic table.
And these are all his original books.
These are his books, written by him.
Oh, I see.
When I say "his books",
not owned by him.
These are the books that he wrote.
Thousands of volumes.
That's impressive.
OK, and if you look at his library,
you will be surprised,
because maybe 10% of the books are
devoted to chemistry and physics
but everything else is economics,
technics, er...
geography, whatever.
He was a polymath.
Yes, and his second wife
was a painter,
and one portrait
here in profile is just by her work.
'Mendeleev had such a breadth
of intellectual curiosity
'he became known as the Russian
Leonardo da Vinci.'
These are the clocks which stopped
at the moment of his death in 1907.
1907, at twenty past six. Yeah.
'It seems as if time has stood still
in this room
'for more than a century.
'And now that I've seen
the inner sanctum
'where Mendeleev puzzled over the
elements, I want to know
'exactly how he pieced together
his masterwork, the periodic table.
'By 1869, Mendeleev had
been trying to find a pattern
'to the elements for a decade.
'Whatever order he and the world's
chemists tried to impose,
'there were still elements
that wouldn't fit.
'A universal theory
seemed out of reach.
'But now Mendeleev hit on a new idea.
'He made up a pack of cards
and wrote an element
'and its atomic weight
on each one.'
Strange though this might sound,
so began the most memorable card
game in the history of science.
He called it chemical solitaire
and began laying out cards just
to see where there was a pattern,
whether it all fitted together.
Now, previously, chemists had grouped
the elements in one of two ways,
either by their properties,
like those that react very strongly
with water,
or by grouping them
by their atomic weight,
which is what
Berzelius and Cannizzaro had done.
Mendeleev's great genius was to
combine those two methods together.
'The odds were stacked against him.
'Little more than half the elements
we now know about
'had been discovered,
' so he was playing with an incomplete
deck of cards.'
He stayed up for three days
and three nights without any sleep,
just thinking solidly
about the problem.
Then, on the 17th of February,
with a snowstorm raging outside,
he decided to stay at home.
He was exhausted,
and he finally he dozed off.
' The story goes he had
an extraordinary dream.
'He saw almost all
of the 63 known elements
'arrayed in a grand table
which related them together.'
It was an incredible breakthrough.
I can imagine Mendeleev feeling like
so many other scientific pioneers.
It's that determination, even
desperation, to crack a puzzle,
and then that
eureka moment of revelation.
Mendeleev had revealed a deep truth
about the nature of our world,
that there is a numerical pattern
underlying the structure of matter.
This is the periodic table
as we know it today,
and it's rooted
in Mendeleev's discovery.
It decodes and makes sense of the
building blocks of the whole world.
Now, although it's so familiar to us,
it's on the wall of every chemistry
lab in every school in the world,
if you really look at it,
it's actually awe inspiring.
What's so remarkable is that it
reveals the relationships
between each and every element
in order.
Mendeleev had brilliantly
combined elements' atomic weights
and properties
into one universal understanding
of all the elements.
Reading it across,
the atomic weights increase step
by step with every element.
But then,
looking at it vertically,
the elements are grouped together
in families of similar properties.
So over on this side are the alkali
metals, from lithium to caesium.
And then over on the far side
are the halogens,
like poisonous chlorine, bromine and
iodine, all very highly reactive.
And alongside them at the top are
the elements important for life -
carbon, nitrogen, oxygen,
all non-metals.
But in the middle, a vast swathe,
are all the metals,
and there are four times
as many metals as non-metals.
Everything is ordered.
It's a chemical landscape
and a perfect map of the geography
of the elements.
'Intriguingly, the periodic table
didn't always look like this.
'Professor Babaev is keen
to show me a copy
'of Mendeleev's very
first manuscript.'
So, this is the first draft of
Mendeleev's periodic table.
You can see the date, 17th February
1869. And it's in his handwriting.
I can see the crossings out, you
can feel his thought processes.
Some familiar elements here.
I see hydrogen, the lightest
element, all the way to lead.
Yeah, yeah. Now you can see some
familiar groups,
like alkali metals, halogens.
It's got lithium, sodium, potassium.
It's not like the periodic table
that I would be familiar with,
it's the other way round.
It took maybe two years
for Mendeleev to bring it
to modern form.
But it's remarkable
that this is the foundations
of the modern periodic table.
It started here.
'Mendeleev's first draft
wasn't perfect.
'To make his table work,
he had to do something astonishing.
'He had to leave spaces for
elements that were still unknown.'
This is a copy of the first published
draft of the periodic table,
and these question marks
are where Mendeleev left gaps.
You see, he was so confident
about his model
that he wouldn't fudge the results.
So where the model didn't work,
he left gaps for elements
that had yet to be discovered.
So, for instance,
this question mark here
he predicted was a metal slightly
heavier than its neighbour calcium.
And here two more metals.
One he predicted would be dark grey
in colour,
and the other would have
a low melting point.
Mendeleev had the audacity to believe
that he would, in time,
be proved right.
It's as if Mendeleev
was a chemical prophet,
foretelling the future
in a visionary interpretation
of the laws of matter.
But before he could claim the glory,
his gaps needed explaining.
And a new way of detecting elements
was invented in 1859.
That was thanks to
Gustav Kirchhoff and his colleague,
the man who made the Bunsen burner.
Robert Bunsen was
a wonderfully intrepid experimenter.
How's this for dedication?
He lost his right eye
in an explosion in his lab.
Now, he knew that when different
elements burned in the flame
of his Bunsen burner,
wonderful colours were revealed.
This one is copper.
This one contains strontium.
And this one is potassium.
Bunsen wondered whether
every element
might have a unique
colour signature,
and so he and Kirchhoff set to work.
Kirchhoff knew that when white light
is shone through a prism
it gets split up into
all its spectral colours...
..all the colours of the rainbow,
from red through yellow
to blue and violet.
And he came up with this.
It's called a spectroscope.
It has a prism in the middle
with two telescopes on either side.
Bunsen and Kirchhoff
then worked together
to analyse different materials
using their new piece of kit.
So they took a compound
containing sodium.
And if I heat it up
in the Bunsen burner,
the light from the sodium
passes through the first telescope
and gets split up by the prism
into its spectral lines.
They then pass through the second
telescope. And if I have a look.
Yep, I can see
the two orange lines
which are the
unique spectrum of sodium.
No other element
would give that pattern.
Using this technique, they actually
discovered two new elements,
silvery-gold caesium,
and rubidium,
so named because of the
ruby-red colour of its spectrum.
It was this same technique that was
used to test
whether Mendeleev's
prediction of gaps was right.
He'd described in meticulous detail
an unknown element that followed
aluminium in his periodic table.
He predicted it would be a silvery
metal with atomic weight 68.
Then, in 1875, a French chemist
used a spectroscope
to identify just such an element -
gallium.
Gallium is a beautiful silvery-white
metal, and it's relatively soft.
Although Mendeleev predicted
its existence,
it was actually found
by Parisian chemist
Paul Emile Lecoq de Boisbaudran.
Gallium has a very low melting point.
And with a boiling point
of 2,204 degrees centigrade,
it's liquid over a wider range of
temperatures
than any other known substance.
Gallium is used to
make semiconductors.
It's found
in light-emitting diodes, LEDs.
One of gallium's compounds was
shown to be effective
in attacking drug-resistant
strains of malaria.
But even though Mendeleev had left
gaps for gallium and other elements,
his table was not complete.
There was one group
that eluded him completely,
an entirely new family of elements.
The story of their discovery
began with an other-worldly search
for an extraterrestrial element.
In August 1868, a total eclipse
of the sun in India was the moment
that French astronomer Pierre
Janssen had been waiting for.
He knew that it was possible to use
a spectroscope
to identify some
elements in the light of the sun.
But the intensity of sunlight meant
that many elements were hidden.
Janssen hoped to see more
during a total eclipse,
when the sun was less blinding.
As Janssen studied the eclipse,
he discovered a colour signature
never seen before.
He was faced with an unknown element.
The same spectral line was confirmed
by another astronomer,
Norman Lockyer.
He named it helium,
after the Greek sun god,
because he thought that
it could only exist on the sun.
Enter Scottish chemist
William Ramsay,
who linked extraterrestrial
helium to Earth.
Ramsay experimented with a
radioactive rock called cleveite.
By dissolving the rock in acid,
he collected a gas
with an atomic weight of 4
and the same spectral signature
that Lockyer had seen, helium.
Helium is the second most abundant
element in the universe,
after hydrogen.
It was one of the elements
produced just after the Big Bang.
Liquid helium is
used to cool superconducting magnets
for MRI scanners.
Deep-sea divers rely on helium
to counter the narcotic effects
on the brain
of increased nitrogen absorption.
And it was a vital ingredient in the
space race,
used to cool hydrogen
and oxygen for rocket engines.
Before he discovered helium on Earth,
William Ramsay had already separated
a new gas from the air, argon,
with an atomic weight of 40.
Now Ramsay faced a puzzle.
He realised that the new elements
didn't fit the periodic table
and suggested
there must be a missing group,
so his search began.
He found three more gases, which
he named neon, Greek for "new",
krypton, meaning "hidden",
and xenon, "stranger".
The group became known as
the noble gases
because they were unreactive
and seemed so aloof.
This family of gases completed
the rows on the periodic table.
Now, Mendeleev may not have
known about these elusive elements,
but he'd established the unshakeable
idea of elemental relationships.
And so he made sure
that there was a place on his table
for every new element,
no matter when it was discovered.
The periodic table is a
classic example
of the scientific method at work.
From a mass of data,
Mendeleev found a pattern.
It led him to make predictions
that could be tested
by future experiments,
pointing the way for
20th-century scientists
to prove him and his theory right.
By the time he died
at the age of 72,
he was a hero in Russia and
a superhero in the world of science.
His periodic table
was immortalised in stone
here in the centre
of St Petersburg,
and he eventually had an element
named after him, mendelevium,
as well as a crater,
the Mendeleev Crater,
on the dark side of the moon...
..fitting tributes to a man who
came from the Siberian wastelands
to become the ultimate
cartographer of the elements.
The periodic table had
finally created order out of chaos.
But it tells us nothing about
WHY our world is as it is,
why some elements are energetic,
others are slow, some inert,
others volatile.
It would be another 40 years
before an entirely different branch
of science came up with an answer.
In 1909, Ernest Rutherford looked
inside the atom for the first time.
Rutherford proposed that
the structure of the atom
was like a miniature solar system,
an overwhelmingly empty space
with a few tiny electrons
orbiting randomly around a dense,
positively-charged nucleus.
But it wasn't until Niels Bohr
came along, one-time goalkeeper
for the Danish football squad and
future Nobel prize-winning physicist
that things really kicked off.
He suggested that the electrons
orbited around the nucleus
in fixed shells.
And it was his idea that was to lead
to the discovery that these shells
could only accommodate
a set number of electrons.
Imagine this football pitch is an
atom, a single atom of an element.
This is the nucleus.
If this nucleus were to scale,
my nearest orbiting electrons
would be beyond the stands,
so I've scaled it down.
Here, on the shell
nearest to the nucleus,
there can be just two electrons,
then it's full.
Here in the second shell,
there can be eight electrons,
then it's fully occupied, too.
The third shell is happy with
18 electrons. And so it goes on.
Outer shells can accommodate an
increasing number of electrons.
So electrons sit in discrete shells,
never in-between the shells.
Bohr's theory would explain
WHY elements behave as they do.
It turns out that it's all to
do with the number of electrons
in the outermost shell.
So, for example, Bohr's model showed
that sodium has eleven electrons -
two here, eight here
and just one in its outer shell.
And fluorine has nine - two here
and seven in its outer shell.
To be completely stable,
atoms like to have a full
outer shell of electrons.
So a sodium atom would
like to lose an electron,
to have a completely
full outer shell,
whereas a fluorine atom has a gap
in its outer shell,
so by gaining an electron
it can complete it.
In this way, a sodium atom and a
fluorine atom can stick together
by exchanging an electron,
making sodium fluoride.
Bohr's work and that
of many other scientists
in the early part
of the 20th century
led to an explanation of every
element and every compound,
why some elements react together
to make compounds
and why others didn't,
why the elements had the
properties that they did,
and this in turn
explained why the periodic table
had the shape that it did.
Mendeleev had managed to reveal
a universal pattern
without understanding
why it should be so.
To find the answer, physicists had
to delve into a subatomic world
that Mendeleev
didn't even know existed.
This work was nothing
short of a triumph.
Even Albert Einstein was impressed.
He wrote, "This is the highest
form of musicality
"in the sphere of thought."
But there was still one
fundamental question left to answer.
How many elements were there?
Could there be an infinite number
between hydrogen,
with the lightest atomic weight,
and uranium,
the heaviest known element?
In the early 20th century,
a brilliant young English physicist,
Henry Moseley,
was determined to find out.
He speculated that the secret
lay within the nucleus
at the heart of each atom.
Moseley developed a unique way
of studying atoms.
Scientists still use
a similar technique today,
although this X-ray spectrometer
looks a bit different to the sort
of kit Moseley that would have used.
One of the elements that he studied
was copper,
and there's a small piece
of copper inside here.
Now, behind it
is a radioactive source
that fires high-energy radiation
at the copper atoms.
Moseley knew that the nucleus
of the atom
contains positively-charged
particles we call protons.
He also knew that surrounding
the nucleus
are negatively-charged electrons.
Now, the radiation being fired at
the copper
is knocking some of the electrons
from the atoms,
and this had the effect
of making the atoms give off
a burst of energy, an X-ray.
And Moseley
found a way of measuring it.
He made a startling discovery.
He found that copper atoms always
give off the same amount of energy.
On this graph,
it's shown by this spike.
And no matter how many times
I repeat this experiment,
I will always get
the spike in the same position.
It's unique to copper.
Mosley also
experimented with other elements.
And inside this sample
there are several others.
So if I move this on
to the next one,
which is rubidium,
and run this again,
I get another spike
in a different position.
And if I move it on again to the
next one, which is molybdenum,
I see a third spike
in a new position.
Every element has its own
energy signature.
But his stroke of brilliance
was to realise
that this is related
to the number of protons.
He was the first person to measure
the number of protons
in the nucleus of an element,
the atomic number.
Atomic numbers are whole numbers,
so, unlike atomic weights,
there can't be
any awkward fractions.
For example, chlorine
has an atomic weight
that comes
in an inconvenient half, 35.5,
but a whole atomic number, 17.
So Moseley realised
that it's the atomic number,
not the atomic weight,
that determines the number
and the order of the elements.
And this is where it gets
really clever.
Because the atomic number
goes up in whole numbers,
there could be no extra elements
between element number one,
hydrogen,
and number 92, uranium.
92 elements is all there could be.
There's just no more room.
So Henry Moseley did the groundwork
that enables us to say
with absolute confidence
that there are 92 elements,
from hydrogen
all the way to uranium.
Mosley was just 26 when he
completed his research,
but his genius
was lost tragically early.
At the outbreak of World War I,
he volunteered to fight,
even though, as a scientist,
he could have avoided joining up.
He was killed in action aged just 27,
shot through the head by a sniper.
A colleague wrote, "In view of what
he might still have accomplished,
"his death might well have been
the single most costly death
"of the war to mankind."
The periodic table is a wonderful
fusion of chemistry and physics.
Mendeleev and the chemists worked
from the outside,
with the chemical properties
of each element,
and the physicists
worked from the inside,
with the invisible world
of the atom.
And yet
both had arrived at the same point.
The ordered design of the natural
world had finally been explained
in a pattern of pure,
intellectual beauty.
So an era that had begun
with scientists groping
towards an understanding
of the basic building blocks
of our world
had ended with
that world entirely classified
and made clear for all to see.
And we never looked back.
Next time, I'll follow
in the footsteps of the chemists
who laboured
to control the elements
and combine them
into the billions of compounds
that make up the modern world...
..I'll discover how
modern-day alchemists
are attempting to push
at the wildest outposts
of the periodic table
to create brand-new elements,
and I'll find out how the power
of the elements was harnessed
to release
almost unimaginable forces.
Subtitles by Red Bee Media Ltd