Answer :
Final answer:
The formal charge on the nitrogen atom in the cyanide ion (CN-) is 0. This is determined based on its triple bond with carbon, its group on the periodic table, and the overall charge of the ion.
Explanation:
The formal charge on the nitrogen atom in the cyanide ion (CN-) can be determined using the formula for formal charge which is:
Formal Charge = (Valence electrons) - (Non-bonding electrons) - (Bonding electrons / 2)
In the cyanide ion, the nitrogen is triple-bonded to carbon and has one lone pair of electrons. Nitrogen, being in group 15, has five valence electrons. There are no non-bonding electrons on nitrogen in cyanide because its lone pair is involved in the pi bonding of the triple bond. It is involved in three bonds (each bond provides two electrons, counting one electron from nitrogen for each bond).
Therefore, the formal charge calculation for nitrogen in the cyanide ion is:
(5 valence electrons) - (0 non-bonding electrons) - (6 bonding electrons / 2) = 5 - 0 - 3 = +2
However, because cyanide has an overall charge of -1 and carbon, being less electronegative than nitrogen, will more likely bear the positive charge, the nitrogen will actually have a formal charge of 0. Nitrogen gains electron density through the triple bond with carbon, thus balancing its formal charge.
