# Relative orbital energies of Mn and Ni

In this MO diagram, why are the atomic Mn $3d$ orbitals higher in energy than the Ni $3d$ orbitals?

• Those elements are in the same period, but nickel has a higher atomic number and therefore greater effective nuclear charge. – Zhe Jun 28 '17 at 15:20
• Higher effective nuclear charge means increased stabilization of electrons. – Zhe Jun 28 '17 at 17:27