Question

In iso-electronic species $O^{2-}$, $F^{-}$ and $N{a}^{+}$, size is affected by:

• A. Nuclear charge (Z) of the element
• B. Valence principal quantum number
• C. Electron-electron interactions in the outer orbitals
• D. None of the factors because their size is the same

Answer 1

The correct option is A Nuclear charge (Z) of the element

Size of an iso-electronic species increases with a decrease in the nuclear charge Z.
The order of increasing nuclear charge is: $O^{2-}$ < $F^{-}$ < $N{a}^{+}$
So the order of increasing size is:
$N{a}^{+}$ < $F^{-}$ < $O^{2-}$