What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group ?

What are the various factors due to which the ionization enthalpy of t

1.	What are the various factors due to which the ionization enthalpy of the main group elements tends to decrease down a group ?
Answer» Solution : Within the main group elements, the ionization enthalpy decreases regularly as we move down the group. This is due to the following FACTORS : (i)Atomic size : On moving down the group, there is a gradual increases in atomic size due to an additional main energy shell (n). (ii) Shielding effect : There is increases in shielding effect on the outermost electron due to increase in the number of inner electrons. (III) NUCLEAR charge : In going from top to bottom in a group, the nuclear charge increases. The effect of increase in atomic size and the shielding effect is much more than the effect of increases in nuclear charge. As a result, the electron becomes less TIGHTLY held to the nucleus as we move down the group. Hence there is a gradual decrease in the IONISATION enthalpies in a group.