Transition and InnerTransition Elements - Result Question 81

####7. The lanthanide ion that would show colour is

(2019 Main, 8 April I)

(a) $Gd^{3+}$

(b) $Sm^{3+}$

(c) $La^{3+}$

(d) $Lu^{3+}$

Show Answer

Solution:

  1. The lanthanide ion that would show colour is $Sm^{3+}$. Colour of a compound depends on the number of electrons in $4 f$-orbitals. Electronic configuration of given lanthanides are as follows:

$$ \begin{aligned} Gd^{3+} & =4 f^{7} \ Sm^{3+} & =4 f^{5} \ La^{3+} & =4 f^{0} \ Lu^{3+} & =4 f^{14} \end{aligned} $$

$Gd^{3+}$ have half-filled $4 f$-orbitals.

$La^{3+}$ have no electron in $4 f$-orbitals.

$Lu^{3+}$ have fully-filled $4 f$-orbitals.

Only $Sm^{3+}$ contain $4 f^{5}$. The electrons can easily undergoes excitation. That result in a formation of colour.



जेईई के लिए मॉक टेस्ट

एनसीईआरटी अध्याय वीडियो समाधान

दोहरा फलक