Q. How many unpaired electrons are present in $ [Cr(NH)_{3}]Br_{3} $
Jharkhand CECEJharkhand CECE 2006
Solution:
$ [Cr(NH_{3})_{5}]Br_{3} $
Suppose oxidation state of $Cr$ is $ x, $
then. $ x+(5\times 0)+(-1\,\times \,3)=0 $
$ x-3=0 $
$ x=+\,3 $
$ {}_{24}Cr=1s^{2},2s^{2}2p^{6},3s^{2}3p^{6}3d^{5},4s^{1} $
$ Cr^{3+}=1s^{2}2s^{2}2p^{6},3s^{2}3p^{6}3d^{3} $
So, three unpaired electrons are present in
$ [Cr(NH_{3})]Br_{3}. $
