3 Rank the following elements in order from smallest to larg

3. Rank the following elements in order from smallest to largest first ionization energy.

  N^3-   O^2-   Mg²⁺   F^-   Na⁺

Solution

  N^3- , O^2- , Mg²⁺ , F^- , Na⁺ have same no of electrons i.e.10

Higher the negative charge, bigger the species.

Higher the positive charge , smaller the species.

Hence,

Order of size from smallest to largest : Mg²⁺ < Na⁺ < F^- < O^2- < N^3-

As atomic radius increases, 1st ionisation energy decreases. Because, electrons are far away from the nucleus.

Therefore,

order of first ionization energy from smallest to largest :   N^3- < O^2- < F^- < Na⁺ < Mg²⁺