Can carbon form four bonds with another carbon?
The only possibility for a quadruple bond between two carbon atoms would be the C2 molecule, as no other bonding to additional atoms would be possible. And C2 is only doubly bonded:
.. or is it? http://www.rsc.org/chemistryworld/news/2012/january/carbon-carbon-quadruple-bond.asp
I stand corrected. Thanks for the link.
I wouldn't consider this "long-bond" a real bond as it is also much weaker than a true bond. But as it is only a concept you are of course free to do so.
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