[plyrjohn404]

How does orbital overlap make molecules more stable than their constituent atoms?

[Schrödinger]

When u consider the MO theory (Molecular Orbital theory), then the constructive interference of the atomic orbitals of each atom results in bonding orbitals of lower energy than the corresponding atomic orbitals themselves. So, they are more stable (Lower position in the Energy Diagram)

When they undergo destructive interference, then Anti Bonding orbitals are formed , which gives rise to molecular orbitals of greater energy than the corresponding atomic orbitals. So , they are less stable. (Higher position in the Energy Diagram).

I think this should help u....