Question

Which of the following order of radii is correct?

• A. $Li<Be<Mg$
• B. $H^{+}<L{i}^{+}<H^{-}$
• C. $O<F<Ne$
• D. $N{a}^{+}<F^{-}<O^{-2}$

Answer 1

The correct option is B $H^{+}<L{i}^{+}<H^{-}$

$H^{-}=1s^2$
$L{i}^{+}=1s^2$
$H^{+}=1s^0$
$H^{-}\text{and}L{i}^{+}$ are isoelectronic. For isoelectronic species, size of $-ve$ charged ion is greater than $+ve$ charged ion.
$\therefore H^{-}>L{i}^{+}\text{where as}{H}^{+}$ is proton its size will be smaller than other two species.