Chapter 14, Problem 88CP

Bond energy has been defined in the text as the amount of energy required to break a chemical bond, so we have come to think of the addition of energy as breaking bonds. However, in some cases the addition of energy can cause the formation of bonds. For example, in a sample of helium gas subjected to a high-energy source, some ${\text{He}}_{\text{2}}$ molecules exist momentarily and then dissociate. Use $\text{MO}$ theory (and diagrams) to explain why ${\text{He}}_{\text{2}}$ molecules can come to exist and why they dissociate.