NEET2023Chemistryd and f Block ElementsActual
Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A) : Ionisation enthalpies of early actinoids are lower than for early lanthanoids. Reason (R) : Electrons are entering 5 f orbitals in actinoids which experience greater shielding from nuclear charge. In the light of the above statements, choose the correct answer from the options given below:
Options
- ABoth ( A ) and ( R ) are true and ( R ) is the correct explanation of ( A ) .
- BBoth ( A ) and ( R ) are true but ( R ) is not the correct explanation of ( A ) .
- C(A) is true but (R) is false.
- D(A) is false but ( R ) is true.
Correct answer
A. Both ( A ) and ( R ) are true and ( R ) is the correct explanation of ( A ) .
Step-by-step solution
Ionisation enthalpies of early actinoids are lower than early lanthanoids. This is because 5 f orbitals will penetrate less into the inner core of electrons. The 5 f electrons, will be more effectively shielded from the nuclear charge than the 4 f electrons of corresponding lanthanoids.