Electron domain geometry of hcn

In the standard Lewis structure H–C≡N, carbon is the central atom. It has two bonding electron domains and no lone pairs, giving linear electron-domain geometry around carbon. The H–C–N arrangement is also linear in the basic model.

Meaning and context

A triple bond counts as one electron domain for VSEPR because it occupies one region or direction from the central atom. Counting its three shared pairs as three separate domains would give the wrong geometry.

Examples and usage

Carbon has one domain toward hydrogen and one toward nitrogen. The predicted angle is approximately 180°. Nitrogen’s lone pair belongs to nitrogen and is not counted as a lone pair on the central carbon.

What to check

HCN is a highly hazardous substance. This is a structural explanation for a chemistry problem, not a preparation or handling instruction. Use the formula and atom connectivity given in the problem rather than guessing a shape from the total number of electrons.

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