what is lanthanoid contraction what are the consequences of lanthanide contraction

Ouestion . What lanthanoid contraction? What are  consequences of the  lanthanoid contraction?

Lanthanoid contraction:-

The word lathanide come from the Greek words that means ( lathanide = hidden ) the total decrease in the atomic and Ionic  radi from lanthanum to leuitetium is observed in the lanthanolds.this phenomenon is called lanthanoid contraction it is due to the fact that with every additional proton in the nucleus, the corresponding electron goes into a 4 subshell. This is also  diffused to screen the nucleus as  effectively as the more localised Inner shell. Hence, the attraction of the nucleus for the outermost electrons increases steadily with the atomic the  number.

Consequences of lanthanide contraction are :-

1)  Basic  characteristics of oxides and hydroxides Due to the lanthanoid contraction, the covalent nature of La-OH bond increases and hereby, the basic character of oxides and hydroxides decreases from LaOH)3,  to Lu (OH)3

2) Similarity in the size of elements of second and third transition series because of lanthanoid contraction, elements which follow :-

the third transition series are considerably smaller than would otherwise be need. The normal size increases from Sc Y-La  and disappears after lanthanides. Thus, pairs of elements such as Z/Hf, Nb/Ta and Mo/w are almost identical in due to approximately  similar in  size, such pairs have very similar characters which makes their separation difficult. Separation of lanthanoids due to lanthanoid contraction, there is difference in   some properties of lanthanoid such as  solubility degree of hydration and complex formation. These enable difference  the separation of lanthanoids by ion exchange manner .