Ionization energies of atoms and atomic ions

Less familiar aspects of ionization energies of atoms and atomic ions from s, p, d, and f blocks of the periodic table are discussed. Apparent irregularities in the first and second ionization energies of transition metals and rare earth metals are explained in terms of electronic configurations of the ground states. A semiquantitative treatment of pairing, exchange, and orbital energies accounts for discontinuities at half-filled p, d, and f electron shells and the resulting zigzag patterns