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 gt gt IE_1` because it has one
valence electron, while Mg has `IE_3 gt gt IE_2 gt IE_1`,
because it has two valence electrons.
In this case X has `IE_5 gtgt IE_4 gt IE_3 gt IE_2 gt IE_1`
Therefore it has four valence electrons.