identify the attractive and repulsive forces that cause the bond length between two bonded atoms to get longer and shorter as though on a spring.

Question

identify the attractive and repulsive forces that cause the bond length between two bonded atoms to get longer and shorter as though on a spring.

Answer 1

A simplistic answer is electrostatic charges. Unpaired electrons cause atoms with them to attract one another. However, the basic explanation then says they get close to each other but not closer because of the electrostatic repulsion between nuclei. A more sophisticated explanation that better explains observable chemistry comes from considering pseudo forces and the Pauli exclusion principle. I'm not sure you're looking for this kind of depth in an answer so I'll just provide a link http://en.wikipedia.org/wiki/Pauli_exclusion_principle.