Carbon is a fantastically important element.
There are probably, far more molecules that contain carbon, than any other element.
The reason why you can get so many carbon compounds, is that carbon atoms,
form chains very, very easily. Sometimes millions of atoms long. If you just have
atoms that will form one or two bonds then you can't build up huge numbers of
molecules.
If there's no limit to the number of bonds you can make, You can make things
that are really long.
It's like the difference between a lorry; a truck which can pull if you're
lucky, one trailer or perhaps two and a train where you can put as many wagons
or carriages as you want. So you can get really long train,
so it's just the same with carbon.
So carbon it's around us everywhere. We're all carbon, there are lots of carbon
in us, in all the hydrocarbons within our body.
Lots of that structures inside us and many many of the materials
that we use every day.
In fact the majority of us use carbon in the form of fuels every day to get to
work or to go home. Without carbon we couldn't exist.
You're carbon, I'm carbon, We have bones made that of calcium. But the important
parts of our brains contain largely carbon. They contain nitrogen and oxygen
and hydrogen as well, but carbon is the key.
Carbon is one of the very few elements; that has given rise to a whole area of
chemistry. Organic chemistry; the chemistry of carbon compounds, is almost
a separate discipline from some of the areas of chemistry and most of the
molecules that we use for plastics, for pharmaceutical products, for our food are
all carbon compounds. Carbon is an extremely common element but it comes
in a number of different allotropes, so different forms and this one here; this
is actually some charcoal, which is just simple carbon. It's very, very similar and
very very in fresh into it to graphite. You can find lumps of carbon lying
around.
This is a piece here, that I found on a beach, on the northeast of England;
it's a piece of coal. Its not absolutely pure carbon, but it has a very high
proportion of carbon and compared to other stones, of this sort of size,
it's really quite light more recently people have discovered diamonds, and of
course graphite which is the black material that you get in pencils. People
call them lead pencils but they actually contain the form of carbon called graphite
so carbon comes graphite, as diamond, and also as as buckyballs or fullerenes so
the carbon here which is a bit like the graphite; it is very amorphous and
it's very very free-flowing so I'm going to pour a little bit of
carbon out onto the paper so you can see so you can see its a very light powder
and you can see that it's a very very nice, easily maneuverable and a really easy workable material.
The thing that's really exciting is that in the last 20 years people have
discovered new forms of carbon;
now this is extraordinary! People have known of carbon for thousands of years,
even longer, and suddenly in the last 20 years the number of different types of
carbon has grown enormously.
I have a colleague who is a specialist in these new forms of carbon and I went
and asked him for a model and he gave me a whole suitcase of models.
Let me show you.
...
So, what did we get?
First of all, this is a model of graphite. The materials in the middle of pencils and it consists of layers of rings, hexagonal rings of carbon atoms.
That six carbon atoms; and they're joined together in layers.
Can you see here? There are purple bonds in between them.
You can see they're not very strong; one is even broken here. Very recently in the
last 10 years its been discovered that using a piece of sellotape, you can pull
off these layers; and make single sheets of these carbon atoms.
It's called graphene. The 2-2010 Nobel Prize for physics, was given to two
scientists for discovering graphene, There's this structure here; where each
carbon atom is joined to 4 others, in this sort of tetrahedral pattern.
Tetrahedron is this group one in the middle with four rounded, and this–is
diamond; it's really very strong.
Whichever way you squash it, it's strong.
You can't peel off layers of diamond with a piece of sellotape. Diamonds are colorless; and to understand why, you
have to understand; what gives rise to color, and the color of anything
my tie, anything are caused by electrons in the molecules or material and they
absorb energy and go from one level to another. In diamond,
there are bonds between all the carbon atoms that use all the electrons. The
electrons are very tightly bound and none of them can change their energy
state,
so you get no absorption. At least in the visible region of the spectrum.
On the other hand with graphite, the electrons are less strongly bound. In
fact it conducts electricity and it's black because the electrons will absorb
all wavelengths of visible light right from the blue to the red so that it
looks black because none of the light is reflected from it. Inside here we have
the famous molecule, C60 like a football (soccer ball US) 60 carbon atoms and Ray has put a little
one inside here but forget that for a moment.
So you can have this molecule C60 first discovered in the late 1980's.
and only isolated in the early 1990's and there is a very similar
molecule which looks a bit more squashed which is C70. Now these are also colored,
but their color is rather different. Have a look here.
I've got two samples one of C60 and one of C70 both of them dissolved up in the
solvent toluene.
So if you look here C70 is a sort of reddish brown color and C60 in the
solvent has a beautiful color.
I call it purple, other people call it magenta. Back to the box (suitcase)
...
and in here, we have the final form of carbon which are called nanotubes
these are whole tubes; made up of hexagons. You have two sorts one which is
closed at the end and this one here which is open
rather like a basket.
you can put things inside it the final model is graphene this material that you
can peel off graphite with a seller tape sticky tape and the reason that people
get so excited is first of all this is a very thin material
it's only one atom thick and you can react
the carbon atoms on here with all sorts of different molecules
you can make very strong materials you can start making electronics carbon
computers things like that
many people believe that graphene is one of the materials of the future
this is one of and raised exhibits
he uses it in exhibitions to measure electrical conductivity to see if you
take a piece of metal like this coin and you put the two electrodes on there you
can see it conducts electricity all the lights light up and the needle goes
across so he's got different samples
this one here is coal and this is graphite
so there's a track of this is a photo and this is a track of coal between two
metal electrodes and you can see if we put the electrodes on here the coal
doesn't conduct electricity at all
however if we take the graphite and do the same
it conducts electricity not very well but you can see you do get some
electricity going through on this other sheet
he's got a sample of C60 and here of the carbon nanotubes and you can see the
C60 doesn't conduct electricity either the electrons can't jump between one
molecule and the other but when you come to the carbon nanotubes which are long
molecules they conduct electricity really well not quite as well as a metal
but pretty close