The atomic radii of the Period 6 d-metals are
A) smaller than expected, and about the same as the Period 5 d-metals.
B) about the same as the lanthanides.
C) larger than the atomic radii of the Period 5 d-metals.
D) about the same as the Period 4 d-metals.
E) large because of the lanthanide contraction.

Question

Quizplus · Accepted Answer

The atomic radii of Period 6 d-metals are smaller than expected and are about the same as the Period 5 d-metals due to the lanthanide contraction. The lanthanide contraction is the phenomenon where the 4f electrons do not shield the outer electrons effectively, leading to a greater effective nuclear charge on the outer electrons and thus smaller atomic radii. This effect is seen when comparing the atomic radii of Period 5 and Period 6 d-metals, where they are unexpectedly similar.

The Atomic Radii of the Period 6 D-Metals Are