Question

explain anthanoids and lanthanoids contraction​

Answer 1

Actinoid Contraction:-

The gradual decrease in the atomic size i.e., atomic radii and ionic radii with increase in atomic number of actinoid's is known as Actinoid contraction.

Cause of actinoid contraction:-

➯Imperfect shielding of the one 5f-electron by another 5f- electron in the same shell is the main cause of actinoid contraction.

➯Due to poor shielding effect of the 5f electrons, effective nuclear charge increases which causes the contraction in atomic size.

Lanthanoid Contraction:-

The gradual decrease in the atomic size from La to Lu due to increasing nuclear charge and electrons entering inner (n-2) f orbital is known as lanthanoid contraction.

Reasons for lanthanoid contraction:-

➯Atomic size

➯The ionization energy of d-block elements.

➯Difficulty in the separation of lanthanides

➯Effect on the basic strength of hydroxides

➯Complex formation

➯The shielding of f orbitals is weaker than d orbitals so the actinoid contraction is more than lanthanoid contraction.

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