Question

What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
(i) $F^{–}$

(ii) Ar

(iii) $M{g}^{2+}$

(iv)$R{b}^{+}$

Answer 1

Atoms and ions having the same number of electrons are called isoelectronic species.
(i) $F^{–}$ ion has 9 + 1 = 10 electrons. Thus, the species isoelectronic with it will also have 10 electrons. Some of its isoelectronic species are $N{a}^{+}$ ion (11 – 1 = 10 electrons), Ne (10 electrons), $O^{2–}$ ion (8 + 2 = 10 electrons), and $A{l}^{3+}$ ion (13 – 3 = 10 electrons).

(ii) Ar has 18 electrons. Thus, the species isoelectronic with it will also have 18 electrons. Some of its isoelectronic species are $S^{2–}$ ion (16 + 2 = 18 electrons), $C{l}^{–}$ ion (17 + 1 = 18 electrons), $K^{+}$ ion (19 – 1 = 18 electrons), and $C{a}^{2+}$ ion (20 – 2 = 18 electrons).

(iii) $M{g}^{2+}$ ion has 12 – 2 = 10 electrons. Thus, the species isoelectronic with it will also have 10 electrons. Some of its isoelectronic species are $F^{–}$ ion (9 + 1 = 10 electrons), Ne (10 electrons), $O^{2–}$ ion (8 + 2 = 10 electrons), and $A{l}^{3+}$ ion (13 – 3 = 10 electrons).

(iv) $R{b}^{+}$ ion has 37 – 1 = 36 electrons. Thus, the species isoelectronic with it will also have 36 electrons. Some of its isoelectronic species are $B{r}^{–}$ ion (35 + 1 = 36 electrons), Kr (36 electrons), and $S{r}^{2+}$ ion (38 – 2 = 36 electrons).