Question

What is the Lewis structure of calcium carbide?

Answer 1

`Ca^(2+)[:C-=C:]^(2-)`

Explanation:

Around each carbon atom there are 5 valence electrons: 3 from the double bond, and 2 in a lone pair. Given the 2 inner shell electrons, this gives 7 electrons per carbon nucleus. Since, for carbon, `Z=6`, each, carbon bears a formal negative charge, and thus there is a formal `2-` charge on the carbide ion (I was about to say the acetylide ion, but this is `""^(-)C-=C-H`).