11th Class Chemistry Classification of Elements and Periodicity in Properties

  • question_answer 28) What are the factors due to which ionisation enthalpy of the main group elements tends to decrease down the group?


    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.

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