Which one of the following statements related to lanthanons is incorrect ?

Options

A. All the lanthanons are much more reactive than aluminium
B. `Ce(+4)` solutions are widely used as oxidizing agent in volumetric analysis
C. Europium shows `+2` oxidation state
D. The basicity decreases as the ionic radius decreases from Pr to Lu.

Explanation

(a) Lnathnons are less reactive than aluminium due tohigh IP ( Lanthanoid contraction)
(b) `Ce^(+4)` is good oxidizing agent and easily converted into `Ce^(+3)`
(c ) Eu ( 63) `= 4f^(7) 5d^(0)6s^(2) ,Eu^(+2)= 4f^(7)`
(d) In lanthanoids series 'Ce' to 'Lu' ionic radius regularly decreases and covalent character increases and hence basic character of hydroxides decreses.