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 +
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).
