Department of Pre-University Education, KarnatakaPUC Karnataka Science Class 12
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Define Lanthanoid Contraction. - Chemistry

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Define lanthanoid contraction.

What is lanthanoid contraction?

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Solution 1

Lanthanoid contraction:-

With an increasing atomic number in the lanthanoid series, there is a progressive decrease in the atomic as well as ionic radii of trivalent ions from La3+ to Lu3+.

This regular decrease (contraction) in the size of the atoms and ions with increasing atomic number is known as lanthanoid contraction.

Solution 2

Lanthanoid Contraction : In the lanthanoids , the electrons are getting filled in the 4f-subshell. On moving from left to right, the nuclear charge increases and this increase is expected to be compensated by the increase in the magnitude of shielding effect by the 4 f- electrons However,
the f-electrons have very poor shielding effect. Consequently, the atomic and ionic radii decrease from left to right and this is knwon as lanthanoid contraction.

Concept: F-block Elements - The Lanthanoids
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NCERT Class 12 Chemistry
Chapter 8 The d-block and f-block Elements
Q 7 | Page 234
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