The correct increasing order of basic character of `Ce (OH)_3 ,Gd (OH) _3 and Nd(OH)_3` is

Options

A. `Ce(OH)_3 lt Nd (OH)_3 lt Gd(OH) _3`
B. `Gd(OH)_3 lt Ce (OH)_3 lt Nd(OH)_3`
C. `Gd(OH)_3 lt Nd(OH)_3 lt Ce (OH)_3`
D. `Ce (OH)_3 lt Gd(OH)_3 Nd(OH)_3`

Answer

C

Explanation

Due to lanthanoid contraction the size of lanthanoid ions decreases regularly with increase in atomic size. As a result of decrease in size, their covalent character between lanthanoid ion and `OH^-` ion increases from `La^(3+)` to `Lu^(3+)`.
Therefore, the basic character of hydroxides decreases from `La(OH)_3`, to `Lu(OH)_3`.Hence, the correct order of basic character will be
`Gd(OH)_3 lt Nd(OH)_3 lt Ce(OH)_3`.