Question

What is common between given cations and anions : $O^{2-},F^{-},N{a}^{+},M{g}^{2+},A{l}^{3+}$?

• A. All have same ionic radii
• B. All are isoelectronic species having 10 electrons
• C. All of them belong to the third period
• D. The nature of oxides of all the ions is basic

Answer 1

Answer: (B)

All are isoelectronic species having 10 electrons

O and F are in period 2 while Na, Mg and Al are in period 3.

Number of electrons in $O^{2-}=8+2=10,F^{-}=9+1=10,N{a}^{+}=11-1=10,M{g}^{2+}=12-2=10,A{l}^{3+}=13-3=10$

Given ions have same number of electrons thus are isoelectronic species.

Thus the order of atomic radii is: $O^{2-}>F^{-}>N{a}^{+}>M{g}^{2+}>A{l}^{3+}$

All are isoelectronic species having 10 electrons.

option B