# Confusion in half filled or full filled electronic configuration

At the end of electronic configuration, we were taught that, electron orbitals are most stable when they are either fully filled or half filled. E.g., the final valence configuration of chromium is $$\ce{(4s)^1 (3d)^5}$$ and not $$\ce{(4s)^2 (3d)^4}$$. But the final electronic configuration of chlorine is $$\ce{(3s)^2 (3p)^5}$$ and not $$\ce{(3s)^1 (3p)^6}$$.

Why doesn't chlorine follow the half filled or full filled theory?

• +1. I have no idea why you got -2, but a new user like you should be made to feel welcome here. – user1271772 Feb 22 at 15:03

In the case of 3$$d$$ and 4$$s$$ energies, there is an "anomaly" in the ordering, being the 3$$d$$ orbital energy higher than that of 4$$s$$. However, you are comparing the configuration of chromium (with 3$$d$$ and 4$$s$$ orbitals) with chlorine. The valence shell of the latter contains 3$$s$$ and 3$$p$$ orbitals, and the energy of 3$$s$$ orbitals are lower than that of 3$$p$$.