# Does vanadium’s 3d orbital fill before 4s?

My lecture slide says that that’s 3d orbital fills first as there are 5 electrons to fill when you are at 3p6 and so the 3d orbital will have added stability from a a half filed orbital. Hence the slide says the configuration is:
1s2 2s2 2p6 3s2 3p6 3d5 but I thought that the 4s only doesn’t fill first for chromium and copper as one electron goes into the 3d instead? I’m confused because I cannot find this info online .
Original post by Jaystocks
My lecture slide says that that’s 3d orbital fills first as there are 5 electrons to fill when you are at 3p6 and so the 3d orbital will have added stability from a a half filed orbital. Hence the slide says the configuration is:
1s2 2s2 2p6 3s2 3p6 3d5 but I thought that the 4s only doesn’t fill first for chromium and copper as one electron goes into the 3d instead? I’m confused because I cannot find this info online .

https://www.chemguide.co.uk/atoms/properties/3d4sproblem.html
and explicitly, I'll copy one of the links on that page:
http://ericscerri.blogspot.com/2012/06/trouble-with-using-aufbau-to-find.html
Original post by Jaystocks
My lecture slide says that that’s 3d orbital fills first as there are 5 electrons to fill when you are at 3p6 and so the 3d orbital will have added stability from a a half filed orbital. Hence the slide says the configuration is:
1s2 2s2 2p6 3s2 3p6 3d5 but I thought that the 4s only doesn’t fill first for chromium and copper as one electron goes into the 3d instead? I’m confused because I cannot find this info online .

the electronic configuration for Vanadium is is not [Ar]3d5. It's [Ar]3d3 4s2

some speak of stability not of a "half filled orbital", but of a "half filled subshell". but a fully filled subshell is very stable, and 4s2 is a fully filled subshell.

The rule about what fills first doesn't change for any transition metal elements. Some use a rule of thumb "into 4s first, out of 4s first". But technically electrons fill into 3d first. That applies to all from scandium onwards. So all transition metals. Scandium's electronic configuration looks a lot like 4s is filling first. 'cos neutral scandium is [Ar]4s2 3d1. Not [Ar]3d3. And the explanation there offered by Prof Eric Scerri is that for neutral scandium, an elecron goes into 3d, then the next two electrons go into 3d but jump into 4s. It is perhaps hypothesising a bit, but we have Hartree Fock calculations that show 3d lower in energy than 4s from neutral scandium onwards. and we know the electronic configurations.

a graph from a paper by vanquickenborne showing energy levels of neutral elements , see how for potassium and calcium 4s<3d in energy level(so, as per n+l rule). .Whereas from scandium, 3d<4s in energy level.

vanadium is weird not when neutral..

Vanadium is a weird ion. In the sense that V+ has an exceptional electronic configuration. V2+ and other vanadium ions there are fine/normal(not exceptional).

https://www.chemguide.co.uk/atoms/properties/3d4sproblem.html

V+ is weird. It loses one from 4s, and then the remaining one in 4s goes into 3d.

V2+'s electronic configuration looks normal again.