Chapter 7.7, Problem 7.9WE

Interpretation Introduction

Interpretation:

The bond order of super oxide ion (${\text{O}}_{\text{2}}{}^{-}$) and whether it is paramagnetic or diamagnetic should be determined on the basis of molecular orbital theory.

Concept introduction:

According to Molecular orbital (MO) theory,

• The atomic orbitals of the atoms constituted in a molecule are combined to produce new orbitals are called Molecular Orbitals.
• Like atomic orbitals, a molecular orbital can accommodate maximum two electrons and the two electrons must have opposite spins (Pauli Exclusion Principle).
• Relative energy levels of molecules are according to the energy levels of atomic orbitals.
• Order arrangement of electrons in the molecular orbitals is shown below.

  14 and below 14 electrons configuration:

  ${\text{σ1s<σ}}^{\text{*}}{\text{1s<σ2s<σ}}^{\text{*}}{\text{2s<π2p}}_{\text{y}}\cong {\text{π2p}}_{\text{z}}{\text{<σ2p}}_{\text{x}}{\text{<π}}^{\text{*}}{\text{2p}}_{\text{y}}\cong {\text{π}}^{\text{*}}{\text{2p}}_{\text{z}}{\text{<σ}}^{\text{*}}{\text{2p}}_{\text{x}}$

14 above electrons configuration:

${\text{σ1s<σ}}^{\text{*}}{\text{1s<σ2s<σ}}^{\text{*}}{\text{2s<σ2p}}_{\text{x}}{\text{<π2p}}_{\text{y}}\cong {\text{π2p}}_{\text{z}}{\text{<π}}^{\text{*}}{\text{2p}}_{\text{y}}\cong {\text{π}}^{\text{*}}{\text{2p}}_{\text{z}}{\text{<σ}}^{\text{*}}{\text{2p}}_{\text{x}}$

• $\begin{array}{l}\text{Bond order}\text{=}\frac{\text{1}}{\text{2}}\text{×}\text{[number}\text{of}\text{electrons}\text{in}\text{bonding}\text{molecular}\text{orbitlas}-\\ \text{number}\text{of}\text{electrons}\text{in}\text{antibonding}\text{molecular}\text{orbitlas]}\end{array}$

• Paramagnetic species have one or more unpaired electrons in their molecular orbitals.
• Diamagnetic species have no unpaired electrons in the molecular orbitals.