The lanthanide ion that would show colour is :

Options

A. `La^(3+)`
B. `Lu^(3+)`
C. `Gd^(3+)`
D. `Sm^(3+)`

Answer

D

Explanation

`La^(3+)" colourless "(4f^0)" " Gd^(3+)" colourless " (4f^7)`
`Lu^(3+) " colourless " (4f^14)" " Sm^(+3)" yellow "(f^5)` .