3D - 2

why does the electron configuration of Cr end in 4s(1) 3d(5) instead of 4s(2) 3d(4)?

Public Comments

1. certain types of electron configurations are more stable than others the most stable are electron configurations that fill an energy level: like 1s2 or 1s2 2s2 2p6 or any other electron configuration ending in p6 the next most stable are electron configurations that fill an energy sublevel: like 1s2 2s2 or 1s2 2s2 2p6 3s2 3p6 4s2 3d10 the next most stable are electron configurations where the energy sublevel is half full, like: 1s1 or 1s2 2s2 2p3 or 1s2 2s2 2p6 3s2 3p6 4s2 3d5 when you have an atom with 24 electrons, the EXPECTED electron configuration would end in 4s2 3d4, but the actual electron configuration of 24 electrons ends in 4s1 3d5. The 4s1 3d5 configuration has 2 half-filled sublevels whereas the 4s2 3d4 configuration has no special stability at all so it just comes down to stability, the 4s1 3d5 configuration is more stable