What is the electron configuration of Cr 3+?

1 Answer
Dr. Hayek
Nov 30, 2015

#Cr^(3+):1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(color(red)(0))3d^(color(red)(3))#

Explanation:

The atomic number of Chromium is #Z=24#, therefore a #Cr# atom possesses #24# electrons.

#Cr:1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(1)3d^(5)#

Note that it is #4s^(1)3d^(5)# and not #4s^(2)3d^(4)# because a half filled #d# orbital is more stable than a partially filled #d# orbital.

However, the chromium ion #Cr^(3+)# possesses #24e^(-)-3e^(-)=21e^(-)# due to the loss of #3# of its electrons.

Thus, the electron configuration of #Cr^(3+)#is:
#Cr^(3+):1s^(2)2s^(2)2p^(6)3s^(2)3p^(6)4s^(color(red)(0))3d^(color(red)(3))#

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