Which of the following statements relating to molecular orbital (mo) theory is incorrect? in a stable molecule having an even number of electrons, all electrons must be paired. combination of two atomic orbitals produces one bonding and one antibonding mo. a bonding mo is lower in energy than the two atomic orbitals from which it is formed. combination of two 2p orbitals may result in either latex: \sigma σ σ σ σ or latex: \pi π π π π mos. a species with a bond order of zero will not be stable.

The first statement is incorrect

Explanation:

It is not a must condition or mandatory requirement that molecules possessing even number of electrons must have there electrons always paired.

In case of oxygen molecule the molecule has total of 16 electrons but in the molecular orbital diagram there are  two electrons which  are unpaired. Due to these unpaired electrons the oxygen molecule is paramagnetic in nature.

The filling of electrons in orbitals are governed by  extra stability. In case of 2 degenerate molecular orbitals ,the electron filling would always follow hunds rule of maximum multiplicity that is initially one -one electron would only be filled in these two degenerate molecular orbitals.

This happens in order to minimize the inter-electronic repulsion which would arise when the two electrons are in single orbital when they can be in separate orbitals of same energy with same multiplicity. All of this governed by quantum mechanics or the principles of high exchange energy.

Rest other statements are all correct and they clearly are or follow the postulates of molecular orbital theory.

The formation of molecular orbital follows the principle of linear combination of atomic orbital which says that the number of molecular formed would be equal to number of atomic orbitals combining.So 2 atomic orbitals would combine to form 2 molecular orbitals one would be bonding and other would be anti-bonding in nature.

A bonding MO is lower in energy than the energy of combining atomic orbitals .

The combination of p-orbitals can result in formation of two kinds of orbitals know as sigma and pi orbitals.The sigma orbitals are generated by head on overlap of the two p orbitals and pi orbitals are generated by lateral overlap of two p orbitals.

Bond order=[no. of electrons in BMO-no. of electrons in ABMO]/2

so if bond order of a molecule is 0 hence the molecule would not exist.