Question

The first ionization potential of $ Na,Mg,Al,Si $ are in the order:
(A) $ Na < Mg > Al < Si $
(B) $ Na > Mg > Al > Si $
(C) $ Na < Mg < Al > Si $
(D) $ Na > Mg > Al < Si $

Answer 1

Hint: Ionization potential is the amount of energy required to convert an atom into an ion. Analyse the trends of ionization potential along a period and along a group. Also take the electronic configuration into consideration.

Complete step by step solution
First let us see what ionization potential is. Ionization can be referred to as the process of conversion of an atom to an ion by removal or addition of electrons. Ionization potential of ionization energy is the amount of energy required to remove an electron from the valence shell of an atom. First ionization potential is the amount of energy required to remove the first electron from the valence shell.
Here we have elements from first and second groups. As we move along a period, atomic number increases and atomic size decreases so ionization potential increases. As we move along a group, the atomic size increases so ionization potential decreases. It is difficult to remove an electron from a fully filled orbital as compared to a partially filled orbital. The electronic configuration of aluminium is $ 3{s^2}3{p^1} $ and that of magnesium is $ 3{s^2} $ . So ionization enthalpy of magnesium is greater than aluminium because magnesium’s s orbital is completely filled while aluminium’s p orbital is partially filled. So the correct order of first ionization potential is $ Na < Mg > Al < Si $ .
So option A is the correct answer.

Note
In the whole periodic table, helium has the highest first ionization potential and francium has the lowest. Metals have low ionization potential as compared to non-metals because non-metals have a tendency to gain electrons. Ionization energy is expressed in electron volts or joules.