Let's have a look at the next element
now. Well sodium doesn't combine
with nitrogen. It doesn't burn in nitrogen. It doesn't react with nitrogen
from the air.
But it is possible to make a compound
between sodium and nitrogen just not by
combining them directly. Okay so it is possible to make a compound and this
compound is very, very different.
Before, we saw the lithium nitride
and this had the chemical formula that was Li3N
so there were three lithiums and one nitrogen.
Well the compound that we can make between sodium
and nitrogen, not by directly combining the elements though but the
compound that we can get
is called sodium azide and this has one sodium
and three nitrogens. So this is the structure there. All the nitrogens,
the three nitrogens are in a row,
so there's a unit of three nitrogens there with one overall negative charge
and the sodium as usual has lost its electron it's given them to the nitrogens
there
to form a positive ion, sodium plus.
Sodium azide, well watch what happens when we heat up
some sodium azide so in the tube here
we have a small quantity of sodium azide
and this is a white solid. So this is in the bottom of the tube. I'm going to heat
this up.
This is just to make sure that no gases come backwards,
no water comes into the apparatus here but we will be collecting any gases
that are formed by displacing the water in this tube.
So I'm just going to heat up the sodium azide,
so just warming it and you can see that maybe it's just because the air is
expanding a few bubbles have come up,
just keep on heating
and all of a sudden look at the gas that's being formed. We're seeing
a black colour forming in the tube
here. The black colour is actually due to metallic sodium
and the gas that's forming over here
is nitrogen gas. So what's taken place here?
The sodium azide has decomposed
to form sodium and that's the black colour that you're seeing here. We've got
metallic sodium, pure sodium,
maybe it's beginning to react with the glass okay but we're also forming
nitrogen gas. This reaction
has been responsible for saving thousands
of lives and Chris will show us how. So here comes Chris
and with his little car here
well this contains some sodium azide.
The sodium azide is in the steering wheel. It's in the air bag.
Okay, the air bag contains sodium azide
and under the right circumstances we can trigger
the rapid release of that nitrogen gas
to form sodium and nitrogen. The sodium then reacts further with other chemicals
that are added
in there it actually contains essentially sand to react with the
the sodium. The sodium steals the oxygen from that in the way that we've seen
with the glass but this produces a lot of nitrogen gas very, very quickly.
So are you ready for this then Chris okay we'll have a count down from three. Don't
blink otherwise you'll miss it.
This is the decomposition of sodium azide
to initially form sodium and lots of nitrogen gas.
So 3, 2, 1...
and you see Panda is perfectly safe.
Yes okay of course
now that sounds very loud but
believe me apparently if you're unfortunate enough to
actually have one of these things go off
the last thing you're worried about is the noise from the airbag. Okay but as I say
this has saved many, many lives. It needs to go off incredibly quickly
so actually when you hit the airbag it's not blowing up
it's actually going down again, it's deflating so you have a nice soft
landing
on your air bag. So that's the compound formed
between sodium and nitrogen but as I say
we can't make this simply by combining sodium with nitrogen,
quite the reverse, we see that it decomposes on warming
to reform the sodium and releasing this nitrogen gas.