Question

1.Consider the isoelectronic species, Na+, Mg2+, F– and O2-. The correct order of increasing length of their radii is

(i)F– <O2- < Mg2+ < Na+

(ii) Mg2+ < Na+ < F– < O2-

(iii) O2- < F– < Na+ < Mg2+

(iv) O2- < F– < Mg2+ < Na+​

Answer 1

When the electrons are added(M-) to an element it's atomic radius increases due to repulsion among the electrons

When electrons are removed from an orbit the the nuclear force acting on the outer most shell increase s thus reducing it's size

Hence the and is

Mg2+ < Na+ < F– < O2-

I hope this helps ( ╹▽╹ )