Question

$1s^2$ is not the electronic configuration of:

• A. hydrogen ion
• B. hydride ion
• C. helium atom
• D. uni-positive ion of lightest metal atom

Answer 1

The correct option is A hydrogen ion

Configuration of $H^{+}=1s^0$.
Configuration of $H^{-}=1s^2$.
Configuration of $H{e}^{+}=1s^1$ and of $Heatom=1s^2$.
Configuration of uni-positive ion of lightest metal i.e. $L{i}^{+}=1s^{2}2s^0$.