Question

The formation of the oxide ion $O^{2-}\left(g\right)$ requires first an exothermic and then an endothermic step as shown below
$O\left(g\right)+e^{-}\to O^{-}\left(g\right);△H^o=-142kJmo{l}^{-1}$
$O\left(g\right)+e^{-}\to O^{2-}\left(g\right);△H^o=-844kJmo{l}^{-1}$
The correct statement is:

• A. Oxygen is more electronegative
• B. $O^{-}$ ion has comparatively larger size than oxygen atom
• C. $O^{-}$ ion will tend to resist the addition of another electron
• D. Oxygen has high electron affinity

Answer 1

The correct option is B $O^{-}$ ion has comparatively larger size than oxygen atom

For size comparison

${\left(\frac{Z}{e}\right)}_0=\frac{8}{9}$

Where $Z\to$ Atomic Number.

$e\to$ Number of $e-$

$\left({\frac{Z}{e}}_0\right)=\frac{8}{8}$

$\therefore \left({\frac{Z}{e}}_0\right)<\left({\frac{Z}{e}}_0\right)$

$\therefore (size{)}_0>(size{)}_0$