Consider the given species: `N^(3-),O^(2-),F^(-),Na^(+),Mg^(2+) and Al^(3+)`
(1) What is common in them?
(2) Arrange them in the order of increasing ionic radii.

Explanation

(1) Each of the given ions has 10 electrons. Hence, they are all isoelectronic species.
(2). Ionic radii of isoelectronic ions decrease with increase in the magnitude of the nuclear charge. Order of increasing nuclear charge of the given isoelectronic ions is `N^(3-) lt O^(2-) lt F^(-) lt Na^(+) lt Mg^(2+) lt Al^(3+)`.
thereofre, order of increasing ionic radii is
`Al^(3+) lt Mg^(2+) lt Na^(+) lt F^(-) lt O^(2-) lt N^(3-)`.