What is the Lewis structure of HCN?
The nitrogen nucleus has 3 electrons from the triple bond, and 2 electrons from its lone pair, and 2 inner core electrons; the associated charge balances the 7 protons in the nitrogen nucleus, so the nitrogen is formally neutral.
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
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