Question

Arrange the ions F^- , O^2- and N^3- in the increasing order of their ionic radii. Give reason.

Answer 1

F^- , O^2- and N^3- are isoelectronic species.

Ions	F-	O2-	N3-
Number of nuclear charge	10	10	10
Number of nuclear charge	9	8	7

The anion with the greater negative charge will have a larger radius because of the lesser attraction of the electrons to the nucleus. 

Hence the increasing order of ionic radii is,

r_Na^3- > r_O^2- > r_F^-