Why is the electron configuration of chromium?
1 Answer
It is energetically favored.
Explanation:
Looking at the periodic table, you would expect Chromium to have this configuration:
Or, condensed using noble gases:
However, the actual configuration of Chromium is:
So why is this? It has to do with main the arrangement of sublevels in the electron cloud. Even though
This happens in Chromium, as one
- The
3d orbital is slightly lower in energy, and minimizing repulsions in the4s orbital by moving one of the4s electrons to a close-lying3d orbital minimizes the ground-state energy of chromium. - Hund's Rule: It is energetically favorable to maximize the spin state in a sublevel. Since two opposite spins result in a total spin of
0 , maximizing this tends to require as many electrons in of same spin in different orbitals as possible. So, in this case, an electron moves to3d and is unpaired, therefore maximizing the spin state.
You will see a similar situation where an
Copper:
Silver:
And gold:
In all of these scenarios, the new redistribution of the electron is energetically favorable compared to the predicted configuration.