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) ${Mg}^{2+}$ iv) ${Rb}^{+}$

Answer 1

Isoelectronic species are the have same number of electrons but different magnitude of nuclear charge and belongs to different atoms.

The isoelectronic ions with greater nuclear charge will have small size as compared to the ions with smaller nuclear charge.

$\left(1\right)F^{-}=9+1=10electrons$,

Thus, the species isoelectronic with also have 10 electrons.

i.e.,

$N{a}^{+}=11-1=10$

$O^{2-}=8+2=10$

$\left(2\right)Ar=18electrons.$

Thus the species isoelectronic with it will also have 18 electrons. Some of its isoelectronic are

$S^{2-}=16+2=18$

$K^{+}=19-1=18$

$\left(3\right)M{g}^{2+}=12-2=10electrons.$

Thus the species isoelectronic with it will also have 10 electrons. Some of its isoelectronic are

$F^{-}=9+1=10$

$A{l}^{3+}=13-3=10$

$\left(4\right)R{b}^{+}=37-1=36electrons.$

Thus the species isoelectronic with it will also have 36 electrons. Some of its isoelectronic are

$B{r}^{-}=35+=36$

$Kr=36$

This is required answer.