Question

In the lewis dot structure for \(NO^{-}_{2}\), total number of valence electrons around nitrogen is .......

Answer 1

Correct Answer: 8

Number of valance e^- around N - atom = 8

Answer 2

Step 1: Write the given ion and determine total valence electrons
For the nitrite ion \( \text{NO}_2^- \):

• Nitrogen (N) has 5 valence electrons.
• Each oxygen (O) has 6 valence electrons → 2 × 6 = 12.
• The extra negative charge (–1) adds one more electron.

Hence, total valence electrons = 5 + 12 + 1 = 18 electrons.

Step 2: Draw possible Lewis structure and bonding
To satisfy the octet rule and the charge, the stable structure has one double bond and one single bond with resonance: O=N–O ↔ O–N=O.
In both resonance forms, the nitrogen is the central atom bonded to two oxygens, one by a double bond and one by a single bond (with an extra lone pair distributed due to resonance).

Step 3: Count the valence electrons around nitrogen
In either resonance structure, nitrogen has:

• Two electrons from the single N–O bond (1 σ bond)
• Four electrons from the double bond (1 σ + 1 π bond)
• Two nonbonding electrons (one lone pair)

Thus, total electrons around nitrogen = 2 (from single bond) + 4 (from double bond) + 2 (lone pair) = 8 electrons.

Step 4: Final reasoning and verification
This satisfies nitrogen’s octet rule. Both resonance forms confirm that nitrogen has a complete octet.

Final answer

8