Question

How do we write the Lewis structures of cyanide, and isocyanide ions?

Answer 1

Typically, we represent the negative charge on CARBON.........

Explanation:

The typical Lewis structure for cyanide anion is `""^(-):C-=N:`; i.e. the carbon centre is associated with 7 electrons, and is therefore a formal anion. Certainly in the parent hydrogen cyanide, the (acidic) hydrogen is bound to carbon, i.e. `H-C-=N`

When cyanides are used (in my opinion, VERY DESTRUCTIVELY) to extract metal ores, for instance those of gold according to the later equation, certainly the carbon centre is the atom that coordinates to gold:

`4 Au + 8 NaC-=N + O_2 + 2H_2O rarr 4{Na^(+)""^(-)[Au(C-=N)_2]} + 4NaOH`

For `"isocyanide"`, `R-N^(+)-=C:^-`, the nitrogen centre is formally cationic with no lone electron pairs available for donation.