Question

Select the correct options:

• A. Due to lanthanide contraction $Zr$ and $Hf$ have almost equal size.
• B. $d$- and $f$-orbitals do not shield the nuclear charge very effectively.
• C. Both (A) & (B) are correct statements.
• D. Both (A) & (B) are incorrect statements.

Answer 1

The correct option is C Both (A) & (B) are correct statements.

The size of neutral atoms of the d-block elements gradually decreases from left to right across a row, due to an increase in the effective nuclear charge (Zeff) with increasing atomic number. In addition, the atomic radius increases down a group, just as it does in the s and p blocks. Because of the lanthanide contraction, however, the increase in size between the 3d and 4d metals is much greater than between the 4d and 5d metals.
Because of the lanthanide contraction, the second- and third-row transition metals are very similar in size.