Question

Which of the following order of atomic / ionic radius is not correct ?

• A. F <Cl< Br <I
• B. Y3+>Sr2+>Rb+
• C. Nb$\approx$ Ta
• D. Li > Be > B

Answer 1

Answer: (B)

Y3+>Sr2+>Rb+

Answer 2

Atomic radius increases on moving top to bottom in a group due to increasing number of shells. However, it decreasing on moving left to right in a period due to increasing Zeff and addition of electrons to the same shell.

Nb (4d) $\approx$Ta (5d) (due to poor shielding of nuclear charge by 4f electrons).

For isoelectronic species, ionic radius $\propto$ $\frac{1}{nuclearch\arg e}$.

So correct order is Y3+ < Sr2+ < Rb+.