Hafnium ionization energy

Fig. 3. The ionization energy of the 4f shell in oxides (empty cirdes), fluorides (squares) and other compounds (filled circles) of lanthanides, hafnium and tantalum. The effects of spin-pairing energy are compared with values of I derived from the calculated uncorrected optical electronegativities (116) for M(IV) and given as full curves appropriate for the ionization of M III). The dashed lines connect the iso-electronic 4f and 4f systems with differing oxidation state.

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