Question

The ions $N^{3-},O^{2-},F^{-},{Na}^{+},{Mg}^{2+}$ are isoelectronic. Their ionic radii shows:

• A. an increase from $N^{3-}$ to $F^{-}$ and then decrease from ${Na}^{+}$ to ${Mg}^{2+}$
• B. a decrease from $N^{3-}$ to $F^{-}$ and then increase from ${Na}^{+}$ to ${Mg}^{2+}$
• C. a significant increase from $N^{3-}$ to ${Mg}^{2+}$
• D. a significant decrease from $N^{3-}$ to ${Mg}^{2+}$

Answer 1

Answer: (D)

a significant decrease from $N^{3-}$ to ${Mg}^{2+}$

$Ionicradii\propto \frac{1}{effectivenuclearcharge\left(Z_{eff}\right)}$ $\propto \frac{1}{positivecharge}$

Hence, as the negative charge increases, ionic radii increases and with an increase in positive charge ionic radii decrease.

Hence, ionic radii decreases from $N^{3-}$ to ${Mg}^{2+}$