Here we will discuss what are isoelectronic species. Let’s study about the examples of isoelectronic species and how to explain them.

What are isoelectronic species

1. These are the species are the ions of the different elements which have the same number of electrons but different magnitude of the nuclear charge.
2. For example S^2-, Cl^–, Ar and K⁺ ions have 18 electrons. But they are having different nuclear charges +16, +17, +18 and +19 respectively.
3. N^3-, O^2-, F^–, Ne, Na⁺, Mg²⁺, Al³⁺ have 10 electrons. But they are having +7, +8, +9, +10, +11, +12 and +13 nuclear charges respectively.

Variation of ionic sizes of isoelectronic ions

The ionic radii of isoelectronic ions decreases with the increase in the magnitude of nuclear charge.

FAQ’s related with isoelectronic ions

1. Name the species which are isoelectronic with Cl^–

Answer : P^3- , S^2-, Ar and K⁺ are isoelectronic with respect to each other. They all have 18 electrons.

2. Name the species which are isoelectronic which is isoelectronic with Rb⁺

Answer : Rb⁺ has 36 electrons. Hence, the species which are electronic with Rb+ are : Br^– , Kr , Sr²⁺

3. Arrange the following species in the decreasing order : O^2-, F , Ne , Na, Mg²⁺, Al³⁺, Cl –

Answer : O^2-, Ne , Mg²⁺, Al³⁺ are isoelectronic which have equal number of electrons. Nuclear charge on O^2-is +8 , Mg²⁺ = +12 , Al³⁺ = +13 and Ne = +10 . Arranging the species according to decreasing size in the order = O^2-, Ne , Mg²⁺, Al³⁺. Because size is inversely proportional to nuclear charge. Since, the size of the species decreases with the increase in nuclear charge.

Check out the following post on ionic size of cations and anions here :

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