Q.16 As predicted by MO theory, the bond order and magnetic nature of NO+ are:
(D) three and diamagnetic
Discover the bond order and magnetic properties of NO⁺ as predicted by Molecular Orbital (MO) theory, with detailed explanations for all MCQ options.
Correct Answer
The correct option is (D) three and diamagnetic. According to MO theory, NO⁺ has a bond order of 3 and is diamagnetic due to all electrons being paired in its molecular orbital configuration.
MO Theory Basics for NO⁺
NO⁺ forms from neutral NO (15 valence electrons) by removing one electron, resulting in 14 valence electrons. The MO diagram for NO (heteronuclear diatomic) follows the order: σ1s, σ1s, σ2s, σ2s, π2px=π2py, σ2pz, π2px=π2py, σ2pz (core orbitals omitted for valence). For NO⁺, electrons fill: σ2s², σ2s², π2px² π2py², σ2pz² – 10 bonding electrons, 4 antibonding. Bond order = (10 – 4)/2 = 3. No unpaired electrons confirm diamagnetic nature.
Option Analysis
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(A) three and paramagnetic: Bond order is correctly 3, but NO⁺ is diamagnetic (paired electrons), unlike paramagnetic NO with an unpaired electron in π*2px.
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(B) two and diamagnetic: Bond order is underestimated; NO has 2.5, NO⁻ has 2, but NO⁺ has 3 due to electron removal from antibonding π* orbital.
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(C) two and paramagnetic: Matches neither; bond order is 3, and it’s not paramagnetic (neutral NO is paramagnetic with bond order 2.5).
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(D) three and diamagnetic: Correct, as removal of the antibonding electron strengthens the bond (shorter length, higher order) and pairs all spins.
| Species | Valence Electrons | Bond Order | Magnetic Nature | Reason |
|---|---|---|---|---|
| NO | 15 | 2.5 | Paramagnetic | 1 unpaired e⁻ in π* |
| NO⁺ | 14 | 3 | Diamagnetic | All paired |
| NO⁻ | 16 | 2 | Paramagnetic | 2 unpaired e⁻ in π* |
