Chromium and Copper

[Andrea_1H]

Why are Chromium and Copper exceptions to the Aufbau principle?

[Lauren Bui 1E]

For chromium and copper, a completely full (d10) or half full (d5) d sub-level is more stable than a partially filled d sub-level. As a result, an electron from the 4s orbital is excited and rises to a 3d orbital, because this reduces the total energy

[Cassidy Kohlenberger 3D]

They are exceptions because a completely full or a half full d sub-level is more stable than a partially full d sub-level. To make the d sub-level more stable, an electron from the 4s orbital is excited/rises to the 3s orbital. Instead of 3d^4 or 3d^9, we excite an orbital to make 3d^5 of 3d^10.

[Lelija Kazlauskas 3J]

Some atoms, like Chromium and Copper, are more stable when their shells or sub-shells are half-filled/filled with electrons, rather than almost half-filled/filled. These atoms are more stable this way, reaching an overall lower state of energy.

[805097738]

because a fully filled or half filled set of orbitals is more stable so an electron is taken from the higher energy level to make the 3d level more stable

[Marykate Abad 3L]

Their electrons fill and half-fill two subshells, with some electrons in the higher energy level shells