what distinguishes a bonding from an antibonding orbital?

Answer 1

That after the combination of atomic orbitals to form molecular orbitals, it takes energy to put an electron into an antibonding (higher energy) orbital, whereas one gains energy from putting one into a bonding (lower energy) orbital. Also, bonding orbitals tend to overlap one another between the bonded atoms, whereas antibonding orbitals tend to have "nonoverlapping" "keep away from one another" distribution. This leaves out nonbonding orbitals, which may be occupied, but contribute nothing to the energy of bonding.

Answer 2

Energy level is higher for antibonding orbital