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NEETChemistryd and f Block Elements

What is the reason for the lower ionization enthalpies of early actinoids compared to early lanthanoids?

Options

  1. ADifferences in atomic number
  2. BDifferences in metallic radii
  3. CPenetration of 5f orbitals
  4. DFormation of protective oxide layers

Correct answer

C. Penetration of 5f orbitals

Step-by-step solution

It is evident from the behaviour of the actinoids that the ionisation enthalpies of the early actinoids, though not accurately known, but are lower than for the early lanthanoids. This is quite reasonable since it is to be expected that when 5f orbitals are beginning to be occupied, they will penetrate less into the inner core of electrons.

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