What do you understand by isoelectronic species? Name a species that will be isoelectronic with each of the following atoms or ions.
`F^(Θ)`, `Ar` ,`Mg^(2+)`,`Rb^(+)`

Explanation

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 `Na^(+)` ion (11 – 1 = 10 electrons), Ne (10 electrons), `O^(2-)` ion (8 + 2 = 10 electrons), and `Al^(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),` Cl^(-)` ion (17 + 1 = 18 electrons), `K^(+ )` ion (19 – 1 = 18 electrons), and `Ca^(2+)` ion (20 – 2 = 18 electrons).
(iii) `Mg^(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 `Al^(3+)` ion (13 – 3 = 10 electrons).
(iv) `Rb^(+)` ion has 37 – 1 = 36 electrons. Thus, the species isoelectronic with it will also have 36 electrons. Some of its isoelectronic species are `Br^(-)` ion (35 + 1 = 36 electrons), Kr (36 electrons), and `Sr^(2+)` ion (38 – 2 = 36 electrons).