question_answer 1)

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

Answer:

The following factors decrease the ionisation enthalpy in the elements of the main group from top to bottom: (i) Atomic size: Atomic size increases due to addition of a new energy shell. This decreases force of attraction towards nucleus and consequently, ionisation enthalpy decreases. (ii) Screening effect: Due to increase of inner electrons, the shielding effect increases which reduces force of attraction towards nucleus and hence, ionisation enthalpy decreases.