Which of the following ions are colourless in the aqueous solutions ?

Options

A. `La^(3+)` and `Lu^(3+)`
B. `Nd^(3+)` and `Pm^(3+)`
C. `Ce^(3+)` and `Pt^(3+)`
D. `Sm^(3+)` and `Eu^(3+)`

Answer

1

Explanation

Most of the trivalent lanthanoid of compounds except that of `La^(3+)` and `Lu^(3+)` are coloured both in the solide state and in the aqueous solution. The colour of these ions can be attributed due to the presence of unpaired `f-`electrons.