# What is the Lewis structure of HCN?

Cyanide anion, $5$ $+$ $4$ valence electrons: ${\left[: C \equiv N :\right]}^{-}$. There is a formal negative charge associated with this anion. Where does it reside?
The carbon atom has (or shares) 3 electrons from the triple bond, and a lone pair of electrons, which it owns. With 2 inner core electrons, this makes 7 electrons with which it is associated. Since, the atomic number of carbon is $6$, the carbon atom is formally negatively charged.
When I write $H - C \equiv N :$, the carbon atom has a share of 4 electrons, and with 2 inner core electrons it is formally neutral, as is the nitrogen and the hydrogen.