Question

Consider the following species: N^3- , O^2-, F^-, Na⁺, Mg²⁺ and Al³⁺ 

1. What is common in them? 
2. Arrange them in the order of increasing ionic radii.

Answer 1

(a) Each of the given species \((ions)\) has the same number of electrons (\(10\) electrons). 
Hence, the given species are isoelectronic.

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(b) The ionic radii of isoelectronic species increases with a decrease in the magnitudes of nuclear charge. 
The arrangement of the given species in order of their increasing nuclear charge is as follows: 
\(N^ {3-} < O^{ 2-} < F^ - < Na^ + < Mg^{ 2+ }< Al ^{3+ }\)
Nuclear charge = \(+7 +8 +9 +11 +12 +13\) 
Therefore, the arrangement of the given species in order of their increasing ionic radii is as follows: 
\(Al^{ 3+} < Mg ^{2+} < Na^ + < F ^- < O ^{2- }< N ^{3-}\)