Question

Which of the following ion is not diamagnetic?

• A.
• B. Sc³⁺
• C. Mg²⁺
• D.

Answer 1

The correct option is A

$H{e}_2^{+}\Rightarrow$ No. of electrons present = 3; It is paramagnetic going by molecular orbital theory, since configuration is $\sigma 1s^2{\sigma }^{\ast }1s^1$
$S{c}^{3+}\Rightarrow$ Diamagnetic (z = 21) but ionic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^6.$
$M{g}^{2+}\Rightarrow$ Diamagnetic as it shows neon configuration
$O_2^{2-}\Rightarrow$ Following Molecular orbital Theory, the configuration is $KK,\sigma 2s^2,{\sigma }^{\ast }2s^2,\sigma 2p_x^2,\pi 2p_y^2=$
$\pi 2p_z^2,{\pi }^{\ast }2p_y^2={\pi }^{\ast }2p_z^2$