Which of the following species has plane triangular shape

Options

(a) N₃
(b) NO₃⁻
(c) NO⁻₂
(d) CO₂

Correct Answer:

NO₃⁻

Explanation:

Hybridization of NO₃⁻=1/2 (5+0+1-0)
= 6/2=3=sp² hence geometry is trigonal planner.
NO₂⁻ (nitrate ion) also has sp² hybridization and gives a trigonal planner geometry but because there are only two outer atoms, the molecular geometry is bent with <120⁰ bond angles.