Even for the same “two electrons in 2p,” the energy changes with how the spins are arranged—the culprits are the Coulomb integral U and the exchange integral J (Lectures 7 and 9). In ①, you fill the 2p, 3d, and 4f levels with electrons by clicking, and check the accounting of the total energy, Hund’s rules, and high-spin/low-spin states. In ②, you look at the splitting of the levels produced by the ligands (anions)—the ligand field itself—using a point-charge model. The group-theory labels and multiplets (term symbols) are calculated with CrystOD.
Energies are in eV and lengths are in Bohr radii aB. Point groups use international notation (m-3m = Oh, -43m = Td, 4/mmm = D4h). The multiplet decomposition comes from crystod-group --multiplet, and the decomposition of the ligand field into irreducible representations from --ligand-field.