I come from a chemistry background and understand probabilities for electron distributions from wavefunctions applied to atoms but don't understand the wave packet idea.What are they and what is the motivation for them?
As Normalizing the solution to free particle Schrödinger equation says, the solution of the free particle Schrödinger equation is non normalizable plane wave solutions. The answers discuss various ways this can be handled.
One way is to take an infinite sum of wave functions with infinitesimal amplitude that add up to a normalized wave function. This is a wave packet.