The bond order of CO molecule on the basis of molecular orbital theory is:(a) Zero(b) 2(c) 3(d) 1

The bond order of a molecule can be determined using molecular orbital theory by calculating the difference between the number of bonding electrons and the number of antibonding electrons, and then dividing the result by 2.

For carbon monoxide (CO), let's consider the molecular orbital diagram:

Carbon (C) has 6 valence electrons, and oxygen (O) has 8 valence electrons.
In the molecular orbital diagram, there are two molecular orbitals involved: the σ bonding orbital (σ*2p) and the π bonding orbital (π2p).
Filling in the electrons:
Carbon contributes 2 electrons (1 from a 2s orbital and 1 from a 2p orbital) to the bonding orbitals.
Oxygen contributes 6 electrons (2 from a 2s orbital and 4 from 2p orbitals) to the bonding orbitals.
There are no electrons in the antibonding orbitals.
Calculate the bond order:
Bond Order = (Number of Bonding Electrons - Number of Antibonding Electrons) / 2

Bond Order = [(2 + 6) - 0] / 2 = 8 / 2 = 4 / 2 = 2

So, the bond order of the CO molecule according to molecular orbital theory is 2.

Therefore, the correct answer is (b) 2