Question

The first four ionization enthalpy values of an element are 191, 578, 872 and 5962 kcal $mo{l}^{-1}$ Q.1) The number of valence electrons in the element is

• A. 1
• B. 2
• C. 3
• D. 4

Answer 1

The correct option is C 3

The successive ionization enthalpies of an element show a regular increase but when the inert-gas configuration is reached, suddenly there is an abrupt increase.

Thus, the valency of an element is equal to the number of successive ionization enthalpies till regular increase is observed. So, the number of successive ionization enthalpies which show a regular increase are three and hence the valency of the element is 3.