Question

The number of antibonding electron pairs in O₂^2- molecular ion on the basis of molecular orbital theory is

(a) 2

(b) 3

(c) 4

(d) 5

Answer 1

Correct option is (c) 4

Write configuration of O₂²⁻​ according to molecular orbital theory and count number of electron pairs in antibonding molecular orbitals.

O₂²⁻ ​= 8 + 8 + 2 = 18

= σ1s², σ∗1s², σ2s², σ∗2s², σ2p_z²​, π2p_x²​,π2p_y²​, π∗2p_x²​,π∗2p_y^2​

∴ Antibonding electron pairs are

σ∗1s²,σ∗2s²,π∗2p_x²​,π∗2p_y^2​

∴ Total 4 antibonding electron pairs are there.