The total number of anti bonding molecular orbitals, formed from $$2s$$ and $$2p$$ atomic orbitals in a diatomic molecule is ______.

We need to find the total number of antibonding molecular orbitals formed from $$2s$$ and $$2p$$ atomic orbitals in a diatomic molecule.

Molecular Orbital Theory: When atomic orbitals combine to form molecular orbitals, each pair of atomic orbitals produces one bonding and one antibonding molecular orbital.

From $$2s$$ atomic orbitals:

Each atom contributes one $$2s$$ orbital. The two $$2s$$ orbitals combine to form:

• $$\sigma_{2s}$$ (bonding)
• $$\sigma^*_{2s}$$ (antibonding) → 1 antibonding MO

From $$2p$$ atomic orbitals:

Each atom contributes three $$2p$$ orbitals ($$2p_x, 2p_y, 2p_z$$). The six $$2p$$ orbitals (3 from each atom) combine to form:

• $$\sigma_{2p_z}$$ (bonding) and $$\sigma^*_{2p_z}$$ (antibonding) → 1 antibonding MO
• $$\pi_{2p_x}$$ (bonding) and $$\pi^*_{2p_x}$$ (antibonding) → 1 antibonding MO
• $$\pi_{2p_y}$$ (bonding) and $$\pi^*_{2p_y}$$ (antibonding) → 1 antibonding MO

Total antibonding MOs from $$2p$$ orbitals = 3

Total antibonding molecular orbitals = 1 (from 2s) + 3 (from 2p) = 4

Therefore, the answer is 4.