Question

$B{e}^{2+}$ is isoelectronic with which of the following ions?

• A. $H^{+}$
• B. $L{i}^{+}$
• C. $N{a}^{+}$
• D. $M{g}^{2+}$

Answer 1

Answer: (B)

Isoelectronic species contain same number of electrons. $B{e}^{2+}$ contains $2$ electrons.
Among the given options, orily $L{i}^{+}$contains $2$ electrons and therefore, it is isoelectronic with $B{e}^{2+}$.
$H^{+}\to$ no electron, $N{a}^{+}\to 10e^{-}$
$L{i}^{+}\to 2e^{-}$
$M{g}^{2+}\to 10e^{-}$
Hence, $B{e}^{2+}$ is isoelectronic with $L{i}^{+}$.