JEE Main20198 Apr 2019Morning ShiftChemistryd and f Block ElementsActual
The lanthanide ion that would show colour is:
Options
- AL u 3 +
- BL a 3 +
- CG d 3 +
- DS m 3 +
Correct answer
D. S m 3 +
Step-by-step solution
The elements or ions having unpaired electrons show colour. The valence shell electronic configuration of La 3 + and Lu 3 + are 4 f 0   and   4 f 14 respectively. Hence, they are colourless. Gd 3 + is also colourless, this is because, here 4 f orbitals are half filled,hence stable.As such f - f transitions are not possible because they will destroy the symmetry of 4 f and make them unstable. Sm 3 + has the valence shell electronic configuration 4 f 5 , hence, it is coloured due to the presence of unpaired