Many of the discrepancies between lanthanum and the lighter group 3 elements can simply be explained by its larger size, as expected from periodic trends, as it precedes the lanthanide contraction that makes the early period 6 transition metals so similar to their period 5 homologs.
22.
The radii of the period-6 transition metals are smaller than would be expected if there were no lanthanides, and are in fact very similar to the radii of the period-5 transition metals, since the effect of the additional electron shell is almost entirely offset by the lanthanide contraction.
23.
The radii of the period-6 transition metals are smaller than would be expected if there were no lanthanides, and are in fact very similar to the radii of the period-5 transition metals, since the effect of the additional electron shell is almost entirely offset by the lanthanide contraction . [ 2]
