What is the total number of valence electrons present in the nitrite ion, NO₂^-?

To determine the total number of valence electrons, we count the valence electrons contributed by each atom and then include the extra electron due to the negative charge.

Nitrogen belongs to Group 15:

Valence electrons from N = 5

Each oxygen belongs to Group 16:

Valence electrons from O = 6

For two oxygen atoms:

2 × 6 = 12

Total electrons from neutral atoms:

5 + 12 = 17

Since the ion carries a -1 charge:

Add 1 extra electron

Therefore:

17 + 1 = 18

The total number of valence electrons in the nitrite ion is 18. These electrons are distributed in the Lewis structure of NO₂^-, where resonance stabilizes the ion by delocalizing the negative charge over the oxygen atoms.

Total Valence Electrons = 18