In molecular orbital theory, the bond order of a molecule can be calculated using the following formula:Bond order = Number of electrons in bonding orbitals - Number of electrons in antibonding orbitals / 2For CO molecule, the electronic configuration is: 1s ^2, * 1s ^2, 2s ^2, * 2s ^2, 2pz ^2, 2px ^2, 2py ^2, * 2px ^1, * 2py ^0Now, let's count the number of electrons in bonding and antibonding orbitals:Bonding orbitals: 1s ^2, 2s ^2, 2pz ^2, 2px ^2, 2py ^2 Total = 10 electrons Antibonding orbitals: * 1s ^2, * 2s ^2, * 2px ^1, * 2py ^0 Total = 5 electrons Using the bond order formula:Bond order = 10 - 5 / 2 = 5 / 2 = 2.5So, the bond order of CO molecule using molecular orbital theory is 2.5.