How does lanthanoid contraction affect the physical and chemical properties of the elements of lanthanoid series ?

Explanation

Physical properties: i) The L.E. of 5d transition series is more than 3d and 4d transition series: ii) They have high melting and boiling points.
Chemical properties: i) As the size of lanthanoid ions decreases from `La^(3+)` to `Lu^(3+)` , covalent character of the hydroxides increases and hence basic strength decreases. ii) The elements of lanthanoid series readily lose electrons and are thus good reducing agents. iii) The elements of lanthanoid series form oxides and hydroxides of the type `M_2O_3` and `M(OH)_3`. They are basic.