Given below are two statements: Assertion (A): Ionisation enthalpies of early actinoids are lower than early lanthanoids. Reason (R): Electrons entering orbitals in actinoids experience greater shielding from the nuclear charge. In the light of the above statements, choose the most appropriate answer from the options given below:
Both (A) and (R) are True and (R) is the correct explanation of (A).
Both (A) and (R) are True but (R) is not the correct explanation of (A).
(A) is True but (R) is False.
(A) is False but (R) is True.
Assertion (A) is true: The ionisation enthalpies of the early actinoids are lower than those for the early lanthanoids . Reason (R) is also true and correctly explains (A): When orbitals are beginning to be occupied, they penetrate less into the inner core of electrons. Therefore, the electrons experience greater (more effective) shielding from the nuclear charge by the inner core compared to the electrons of the corresponding lanthanoids. Because these outer electrons are more effectively shielded, they are less firmly held by the nucleus, resulting in lower ionisation enthalpies . (Note: It is important to distinguish that while electrons themselves provide poor shielding to other electrons, they experience greater shielding from the inner core).
Join thousands of students and practice with AI-generated mock tests.