Lead compounds electronic screening

The ionic radii of the M3+ and M4+ ions of the actinides decrease with increasing positive charge of the nucleus (the actinide contraction) (Fig. 15.15). This contraction is due to the successive addition of electrons in an inner f shell where the incomplete screening of the nuclear charge by the added f electron leads to a contraction of the outer valence orbital. Because the ionic radii of ions of the same oxidation state are generally similar (Fig. 15.15), the ionic compounds of the actinides are isostructural. 

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