Question

Explain the cause of lanthanoid contraction ?

Answer 1

The lantbanoid contraction is due to the poor shielding effect of 4f electron due to which there is an large extent of irregularities in the properties of F block elements.

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Answer 2

PERIODIC TABLE

Lanthanide Contraction: The steady decrease in the size of lanthanide ions (M3+) with the increase in atomic no. is called lanthanide contraction.

Cause

As we move down the group from left to right in a lanthanide series, the atomic number increases and for every proton in the nucleus the extra electron goes to 4f orbital. there is a gradual increase in the effective nuclear charge experienced by the outer electrons. Consequently , the attraction of the nucleus for the electrons in the outermost shell increases with the increase of atomic number, thus size decreases.