28. Construct a molecular orbital energy diagram for Cr2 using only the 3d orbitals as the basis set. Label each orbital as nb, σ, π, δ, σ*, π*, or δ*. Show that the bond order is equal to 4. How many unpaired spins are there? Sketch the shapes and phase relationships of each of the bonding orbitals; if there are degenerate orbitals, only sketch one orbital of that energy. Hint: although the 4s orbital in Cr is not used in the basis set, the electrons from the 4s orbitals are used in the MO diagram.
The electron configuration is σ2π4δ4δ*2 giving a bond order of ½(10 – 2) = 4 and 2 unpaired spins.