The successive ionzation enegry values for an element `X` are given below:
(i) `1st` ionization enegry `= 410 kJ mol^(-1)`
(ii) `2nd` ionization energy `= 820 kJ mol^(-1)`
(iii) `3rd` ionization enegry `= 1100 kJ mol^(-1)`
(iv) `4th` ionization enegry `= 1500 kJ mol^(-1)`
(v) `5th` ionization enegry `= 3200 kJ mol^(-1)`
Find out the number of valence electrons for the atom `X`.

Options

A. 4
B. 3
C. 5
D. 2

Answer

A

Explanation

The ionisation energies provide an indication about the number of valence electrons in an atom.
For example, Na has `IE_(2)gtgtIE_(1)` because it has one valence electron, while Mg has `IE_(3)gtgtIE_(2)gtIE_(1)`, because it has two valence electrons.
In this case X has `IE_(5)gtgtIE_(4)gtIE_(3)gtIE_(2)gtIE_(1)`
Therefore it has four valence electrons.