Which of the following statements relating to molecular orbital(MO) theory is incorrect?

1.) Combination of two 2p orbitals may result in either sigma(?)or pi(?) MOs.

2.) A species with a bond order of zero will not be stable.

3.) In a stable molecule having an even number of electrons, allelectrons must be paired.

4.) Combination of two atomic orbitals produces one bonding andone antibonding MO.

5.) A bonding MO is lower in energy than the two atomic orbitalsfrom which it is formed.