Is electron removed from 3d or 4s first?

[Louise Zhuang]

For example, for the element Mn, when forming a +1 ion is electron removed from 3d or 4s orbital first? Why?

[Kim Tran 1J]

Orbitals are filled in the lower energy orbitals first, then fill higher energy orbitals. The 3d orbitals have a slightly higher energy than the 4s orbitals. So because the 4s orbitals has the lower energy, it gets filled first.

When 3d orbitals are filled, 4s is no longer lower in energy. Hence electrons are lost from 4s orbital first, because electrons lost first will come from the highest energy level (furthest away from the nucleus).

The 4s sublevel is only lower in energy if there are no electrons in the 3d orbitals

[rkang00]

Does this mean that generally 4s orbitals will lose electrons before 3d electrons are lost?

[Megan Wong 4E]

Yes, electrons will be lost from the 4s orbital rather than the 3d orbital.

In this example, Mn's configuration is 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^2
and Mn +1 would be 1s^2 2s^2 2p^6 3s^2 3p^6 3d^5 4s^1.

[sarahartzell1A]

The electron will be removed from 4s first since 3d has slightly higher energy.

[Julia Jones 1G]

Electrons are first removed from the 4s orbital befofe the 3d orbital.