Carbon

[muskan]

Why carbon doesn't share all it's four electrons with one carbon?

[John Cuthber]

To do that  it would need to pack all the electrons into the space between the two atoms but electrons repel one-another.

On the other hand, in the vapour phase at least some of the carbon atoms go round in pairs. It's not clear that they have a "quadruple bond" between them.

With bigger atoms (where the electrons are not so tightly packed) you can get quadruple bonds.

https://en.wikipedia.org/wiki/Quadruple_bond

 

[Area54]

3 hours ago, John Cuthber said:

On the other hand, in the vapour phase at least some of the carbon atoms go round in pairs. It's not clear that they have a "quadruple bond" between them.

I presume this is a dynamic equilibrium situation. If so, do we know what the average 'lifetime' of a pair is?

[John Cuthber]

It's hard to say.

There's some information here

https://en.wikipedia.org/wiki/Diatomic_carbon

 

But, as far as I can see, there's no reason why a single molecule of the stuff floating in space shouldn't last practically forever.