Chapter 2.4, Problem 1P

Interpretation Introduction

Interpretation:

The molecular orbital diagram for diatomic helium $(H{e}_2)$ is to be constructed and the reason that helium is monoatomic instead of diatomic is to be explained.

Concept introduction:

The molecular orbital theory of chemical bonding describes the structures of the electrons of a molecule.

The MO diagram shows the energy level of the electrons in the molecules.

Bond order of a molecules decides the stability of the molecules. That is, the higher the bond order, the more stable the molecule.

Bond order $=\frac{1}{2}\left({\text{B}}_{{\text{e}}^{-}}-{\text{A}}_{{\text{e}}^{-}}\right)$, here ${\text{B}}_{{\text{e}}^{-}}$ is the number of bonding electrons and ${\text{A}}_{{\text{e}}^{-}}$ is the number of antibonding electrons.