[o1ocups]

How many unpaired electrons would you expect for [Cr(CN)6]4- ?

What I did:

Cr is +2
Cr is 4s1 3d5
so Cr +2 is 4s0 3d4
d4 electronic config.

CN- is a strong-field ligand, so large crystal field splitting energy
electrons will pair up before they go to occupy the higher energy level
so there are no unpaired electrons...

but the answer is not 0
What did I do wrong??   

And it's not 4 either.

[Squirmy]

CN- is a strong-field ligand, so large crystal field splitting energy
electrons will pair up before they go to occupy the higher energy level
so there are no unpaired electrons...

How many lower energy d-orbitals are there? How many electrons can each hold?

[o1ocups]

How many lower energy d-orbitals are there? How many electrons can each hold?

the coordination number of this complex ion is 6 right? so is this octahedral?
there are three lower energy d-orbitals...? i'm looking at my textbook and i think they might be dxy, dyz, and dxz.
so if that's the case there will be 2 unpaired electrons??? is that it?

but if that's right i don't understand why for all the other ones there are 5 orbitals.
sorry i just read this chapter today and it's kind of confusing to me 

[Squirmy]

There are five d orbitals total. For octahedral complexes, there are three lower energy orbitals that are degenerate (same energy) and two higher energy orbitals that are degenerate.

As you said before:

CN- is a strong-field ligand, so large crystal field splitting energy
electrons will pair up before they go to occupy the higher energy level

[o1ocups]

Yeah I get it now  Thanks
I didn't really know what I was talking about before.