Identify the isoelectronic pair of ions from the following.
Identify the isoelectronic pair of ions from the following.
$\mathrm{Pr}^{3+}, \mathrm{Nd}^{3+}$
$\mathrm{Tb}^{3+}, \mathrm{Dy}^{2+}$
$\mathrm{Eu}^{2+}, \mathrm{Gd}^{3+}$
$\mathrm{Pr}^{3+}, \mathrm{Ce}^{4+}$
Solution
Isoelectronic species have same number of electrons in them.
(a) $\mathrm{Pr}^{3+}$ number of electron $=59-3=56$
$\mathrm{Nd}^{3+}$ number of electron $=60-3=57$
$\therefore \mathrm{Pr}^{3+}$ and $\mathrm{Nd}^{3+}$ are not isoelectronic.
(b) $\mathrm{Tb}^{3+}$ : Total number of electron $=65-3=62$
$\mathrm{Dy}^{2+}$ : Total number of electron $=66-2=64$
$\therefore \mathrm{Tb}^{3+}$ and $\mathrm{Dy}^{2+}$ are not isoelectronic.
(c) $\mathrm{Eu}^{2+}$ number of electron $=63-2=61$
$\mathrm{Gd}^{3+}$ number of electron $=64-3=61$
$\therefore \mathrm{Eu}^{2+}$ and $\mathrm{Gd}^{3+}$ are isoelectronic.
(d) $\mathrm{Pr}^{3+}$ number of electron $=59-3=56$
$\mathrm{Ce}^{4+}$ number of electron $=58-4=54$
$\therefore \mathrm{Pr}^{3+}$ and $\mathrm{Ce}^{4+}$ are not isoelectronic.