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The d-And-f-Block Elements
Question
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Reason of lanthanoid contraction is

  • negligible Screening effect of 'f' orbitals

  • increasing the nuclear charge

  • decreasing the nuclear charge

  • decreasing screening effect

Answer

A.

negligible Screening effect of 'f' orbitals

Lanthanoid contraction is the regular decrease in atomic and ionic radii of lanthanides. This is due to the imperfect shielding [or poor screening effect] of f-orbitals due to their diffused shape, which unable to counterbalance the effect of the increased nuclear charge. Hence, the net result is a contraction in size of lanthanoids.

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