3D - 2

Which element has the ground state electron configuration [Ar]4s(^1)3d(^5)?

how can it be 4s(^1) and 3d(^5)? wouldn't it have to go to 4s(^2) first

Public Comments

1. This is a transition metal, in the row that starts with K. It goes to 3d5 4s1 b/c you need to fill all the orbitals in 3d5. There are 6 e- and this allows one e- per orbital. If you did 4s2 then you would have 3d4 which leaves 1 orbitals completely empty, and that is very unstable. This element is Cr.
2. Cr it is one of the exceptions which involve filling of subshells with similar energies.whats happening here is that certain combinations of repulsions between electrons in certain electyron configurations produce minor exceptions in the expected order of filling of these subshells, becausethe energies resulting from the repulsions are greater than the smaller differences in energy between the subshells. So it is 4s1 3d5.