3D - 2

Why is the following electron configuration not possible: 1s^2 2s^2 2p^6 3s^2 3p^6 3d^2 4s^1?

Public Comments

1. It should be 1s^2..................................................... 3d^9 4s^1 The given configuration does not exist because 3d subshell is filled after the complete filling of 4s subshell. Only in exceptional cases,the configuration such as 3d9 4s^1 exists.
2. it does work..
3. according to aufbau's principle..which we learnt in Xth..we know that orbitals with lowest energy are filled first...so the energy of a given orbital is calculated by using (n+l) value....where l is the azimuthal quantum number.... so for 4s n+l=4+0=4 and for 3d n+l=3+2=5 so 4s is filled first with its maximum of 2 electrons........
4. Ground state of Sc: [Ar]3d^14s^2; first excited state of Sc (Sc*): [Ar]3d^24s^1: the transition between these two states will give rise to the lowest energy absorption or emission line in the atomic spectrum of Sc(g) (I think there is a dipole moment change for an s ↔ d transition). So the state is allowed but it is an excited state of Sc.