Question

1. Arrange the following ions in order of increasing ionic radius:
potassium ion, calcium ion, phosphide ion, sulfide ion (smallest to largest)
2. Arrange the following ions in order of increasing ionic radius:
aluminum ion, sodium ion, fluoride ion, nitride ion (smallest to largest)

Answer 1

Q98292

Solution:

1. Ionic Radius : $Ca^{2+}<K^+<S^{2-}<P^{3-}$
2. ionic Radius : $Al^{3+}<Na^+<F^-<N^{3-}$

As, number of electrons are the same in all ions, size difference occurs due to varying nuclear force of attraction. Greater the number of protons in the nucleus ($i.e.$ greater the atomic number), greater the nuclear binding force and thus smaller the ionic radius.