Assertion (A): The atomic and ionic radii generally decrease towards right in a period.

Reason (R): The ionisation enthalpy increases on moving towards left in a period.



  • As we move from left to right in a period, the ionic and atomic radii decrease .
  • Ionization enthalpy is the energy required to remove an electron from an atom . As we move from left to right in a period, as the atomic size decreases, and ionization enthalpy increases .

Modern Periodic table ionic and atomic radii decrease-01 - Teachoo.jpg


  • Assertion is true.
  • Reason is false.

Therefore, the correct option is (c) Assertion is true but Reason is false

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Maninder Singh

CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo