What is the electron configuration of Cr 3+?

1 Answer
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))