Question

What is lanthanide contraction ? What are its consequences ?

Answer 1

Lanthanide Contraction :- The steady decrease in the atomic and ionic size in lanthanides with increase in atomic number due to Peculiar shape and poor shielding effect of f - orbitals is called Lanthanide contraction

Consquences :-

a) 4d and 5d series of elements have nearly same atomic size. Eg : Zr & Hf , Nb & Ta, Mo & W

b) The Crystal structures and other properties of lanthanides becomes almost similar

c ) the melting, boiling points and hardness of lanthanides gradually increases

d) Inert pair effect is also a consequence of Lanthanide contraction

e) The basic strength decreases from $\mathcal{Ce(OH)_{3} \: \: to \: Lu(OH)_{3}}$. It is due to decrease in the size from $\mathsf{{Ce}^{3+} \: \: to \: \: {Lu}^{3+}}$ and increase of covalent character of M-OH bond

Answer 2

The decrease in size of lanthanide ion due to increase in atomic number is known as lanthanide contraction. Consequences of lanthanide contraction: • Hard to separate the lanthanides • Increase in electronegativity • Increase in ionisation energy • Ability of complex formation decreases.