Q17. The O–O bond order in O22- species is
(A) 0.5
(B) 1.0
(C) 1.5
(D) 2.0
The O–O bond order in the O₂²⁻ (peroxide ion) species is 1.0.
This matches option (B) in competitive exams like CSIR NET Life Sciences, where molecular orbital theory determines bonding in diatomic species.
Bond Order Calculation
O₂²⁻ has 18 valence electrons (8 per O atom + 2 extra). The molecular orbital configuration is σ2s² σ2s*² σ2pz² π2px² π2py² π2px*² π2py*², ignoring core 1s orbitals.
- Bonding electrons: 10 (σ2s², σ2pz², π2px², π2py²)
- Antibonding electrons: 8 (σ2s*², π2px*², π2py*²)
Bond order = (10 – 8)/2 = 1
Option Analysis
(A) 0.5
Matches species like H₂⁺ or He₂ with 1 bonding and 1 antibonding electron; too weak for O₂²⁻’s filled orbitals.
(B) 1.0 ✓
Correct for O₂²⁻, indicating a single O–O bond as in peroxides (e.g., H₂O₂).
(C) 1.5
Applies to O₂⁻ (superoxide, 17 electrons, 10 bonding – 7 antibonding).
(D) 2.0
Matches neutral O₂ (16 electrons, 10 bonding – 6 antibonding).
O₂²⁻ Bond Order Calculations for CSIR NET
O₂²⁻ bond order calculations help CSIR NET aspirants master molecular orbital theory for diatomic oxygen species. The peroxide ion features a single O–O bond, contrasting stronger bonds in O₂ or O₂⁺.
Molecular Orbital Diagram Summary
The diagram shows 10 bonding vs. 8 antibonding electrons, yielding bond order 1—diamagnetic and stable in compounds like Na₂O₂. Lower bond order than O₂ (2.0) explains its longer O–O distance (~1.49 Å).
CSIR NET Exam Relevance
| Species | Bond Order | Magnetic Property |
|---|---|---|
| O₂ | 2.0 | Paramagnetic |
| O₂⁻ | 1.5 | Paramagnetic |
| O₂²⁻ | 1.0 | Diamagnetic |
Key Takeaway: This trend predicts stability: higher bond order means stronger bonds.
SEO Details
- Slug: o2-2-bond-order-o-o-peroxide-ion
- Primary Keyword: O₂²⁻ bond order
- Secondary Keywords: peroxide ion, O-O bond order, molecular orbital theory
