Hybridization of CH3CN

[505166714]

For Question8 in 2011 midterm. What is the hybridization of the Nitrogen atom in CH3CN? What about the lone pair on N? Are there different hybridizations for the 3 bonds between the central Carbon atom and the Nitrogen atom? How should I represent the hybridizations in the final if there are questions like this?

[Tessa Lawler 1A]

So if the Nitrogen atom in that molecule has a lone pair and is triple bonded to carbon, then it's hybridization would be sp, because there are two regions of electron density (the triple bond with carbon and the lone pair on Nitrogen itself). The Carbon atom bonded to N has a hybridization of sp, because it has two areas of electron density (its bond with N and it's bond with the central C atom). The central C atom has a hybridization of sp3 for its four regions of electron density.
So, basically. Look for an atom's bonds and lone pairs. A lone pair is always a region of electron density, and counts towards hybridization. A bond is always a region of electron density as well, but it doesn't matter if that bond is a single, double, or even quadruple bond - it can only be counted as one region of electron density. You would add up the number of regions to find the hybridization.

[Matthew Choi 2H]

The hybridization of the N is sp. This is because there are two region of electron density: the triple bond with the C and the lone pair. The lone pair counts as one area of electron density. The triple bond also only counts as one area of electron density despite there being 6 electrons involved. The way that I represented the hybridizations was just by writing the hybridization (e.g. sp3) next to the atom in question on a drawing of the Lewis structure.