CHM 501

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.

Answer

The electron configuration is σ2π4δ4δ*2 giving a bond order of ½(10 – 2) = 4 and 2 unpaired spins.