I don't understand the electrons! X(?

Question

what is the electron configuration for Pr 3+?

is it [Xe]6s^2 or [Xe]4f^2 or [Xe]6s^2 4f^2?

well, first, i thought about the first answer, because since it is Pr 3+, that means it has lost some electrons, so that can't be the third one.

but then...

my tchr taught me that electrons like to have space.if they can have their own room(orbitals), they will.

in this case, i thought that the two electrons left over would rather occupy the empty orbitals 4f than squeezing in one orbital 6s.

I am just not sure.

someone please help me!

Answer 1

It is the second one. [Xe] 4f2

The 6s electron shell is further away from the 4f electron shell....this means that the two electrons from the 6s shell are easier to take away than the 4f electrons. The two 6s electrons are taken away and one of the 4f3 electrons to leave you with  4f^2.