Question

Why two molecular orbitals are formed by combination of two atomic orbitals ? Why not one ?​

Answer 1

The corresponding orbitals of both atoms should have the same symmetric orientation around the molecular axis. Although all the three orbitals of 2p have the same energy, 2pz orbital of one atom can only combine with the 2pz orbital, not 2px or 2py, of the other atom.

Answer 2

Answer:

Two atomic orbitals can overlap to form two molecular orbitals, one of which lies at a lower energy level than the overlapping atomic orbitals and is called a bonding molecular orbitals and the other lies at the higher energy level and is called antibonding molecular orbitals .