Fundamental Reaction Types

Complexation + Decomplexation

When NBE pair bonds to an open-shell atom

Decomplexation when a sigma-bond is broken, and restores a NBE pair, leaving behind an open-shell atom.

Substitution

Sigma-bond is replaced with a different sigma bond, either to create charged atoms or to balance and make neutral atoms.

think Substitution SigmaS Replaced, like substitute teacher

Addition

Pi-bond becomes two sigma-bonds, but electrons need to be brought in from something else to make a second sigma-bond (e.g. another compount like HOCl)

Addition like adding another compound to make new sigma bond

Elimination

2 sigma-bonds become a single pi-bond
(think of it as eliminating redundancy, you are subtracting/eliminating a bond)