Chapter 9, Problem 9.2P

Interpretation Introduction

Interpretation:

The bond order of ${\text{B}}_{\text{2}}$ molecule has to be given.

Concept Introduction:

Molecular orbital theory:

Molecular orbital theory suggests the combination of all atomic orbitals having comparable energy and proper symmetry.

Postulates of MOT is,

• Atomic orbitals of same energy and proper symmetry combine together to form molecular orbitals.
• The movement of electrons in a molecular orbital is influenced by all the nuclei of combining atoms.
• The number of molecular orbitals formed is equal to the number of combining atomic orbital when two atomic orbitals combine two molecular orbitals are formed.  One molecular orbital has high energy than the corresponding atomic orbitals and is called antibonding orbital and the other one with lower energy is called bonding orbital.
• In molecular orbitals, the electrons are filled according to the Pauli’s exculsion principle, Aufbau principle and the Hund’s rule.

Bond order $\text{=}\frac{\left({\text{N}}_{\text{b}}\right)\text{-}\left({\text{N}}_{\text{a}}\right)}{\text{2}}$

Where, ${\text{N}}_{\text{b}}$ is number of electrons in bonding orbital.

${\text{N}}_{\text{a}}$ is number of electrons in antibonding orbital.