What are the main consequences of lanthanoid contraction ?

Explanation

Consequences of lanthanide contraction:
(i) Basicity of ions : Due to lanthanide contraction, the size of `Ln^(3+)` ions decreases regularly with increase in atomic number: According to Fajan.s rule, decrease in size of `Ln^(3+)` ions increase the covalent character and decrease the basic character between `Ln^(3+) and OH^(-)` ion in `Ln(OH)_3`. Since the order of size of `Ln^(3+)` ions are `La^(3+) gt Ce^(3+) gt Lu^(3+)`
(ii) There is regular decrease in their ionic radii.
(iii) Regular decrease in thefr tendency to act as reducing agent, with increase in atomic number.
(iv) Due to lanthanoid contraction, second and third rows of d-block elements (transition elements) are quite close in their properties.