Question

Discuss the consequences of lanthanide contraction.

Answer 1

Lanthanide contraction is a very important phenomenon in determining the characteristics of the elements of lanthanide series. The decrease in size of lanthanide (M) ion due to increase in atomic number is known as lanthanide contraction.

Complete answer:
We should know that in the case of lanthanide elements , it has been experimentally found that with increasing atomic number, the atomic and ionic size of lanthanide elements gradually decreases from lanthanum to lutetium. Lanthanide contraction describes a trend in the atomic radius that is exhibited in the Lanthanide series.

Due to the similar sizes of the lanthanides, it is difficult to separate Lanthanides but Due to lanthanide contraction their properties slightly vary. This variation in the properties is utilized to separate them.
The density of second and third transition metal series are much higher due to lanthanide contraction.
Ionic radii decrease regularly and ionic radii of lanthanides decreases from 103 pm ($L{a^{3 + }}$) to 86 pm $(L{u^{3 + }})$ in the lanthanide series.
Due to lanthanide contraction, second and third rows of d-block elements (transition elements) are about the same.
Lanthanide contraction is a significant factor in terms of chemical similarity of zirconium and hafnium of the periodic table. Because of the lanthanoid contraction, hafnium possesses a radius nearly the same to the lighter zirconium.

Additional Information: Lanthanoid contraction is also called lanthanide contraction. The Lanthanide Contraction is the result of the poor shielding effect of 4f electrons. Because of this lanthanoid contraction, the heavier hafnium, which immediately follows the lanthanides, possesses a radius nearly identical to lighter zirconium.

Note: The most important point to be noted is that f-block elements are called inner transition elements. Lanthanides and actinides are the 4f and 5f orbitals that are present in the periodic table. Actinides are metals, soft but tarnish in air. They have high density as compared to the lanthanides. In the periodic table, 57-71 atomic number elements are called lanthanides whereas atomic numbers from 89 to 103 are the actinides.