[unsu]

Does anyone know how to derive a term symbol for a Cr atom?
Because its configuration is 4s(1)3d(5)
To get a term symbol we must consider a sub-shell with a specific value of l.
In Cr atom there are two unoccupied orbitals with l=0 and l=1
So, any idea how to derive a term symbol for Cr?

[Corribus]

The same way you do any other electron configuration. Are you familiar with how to determine term symbols - generally?

[unsu]

oookk... then:

4s(1)3d5
M_L = 0 + 2 + 1 + 0 + (-1) + (-2) = 0
L = S
max M_s = 6*(1/2) = 3
S = 3
Ground state configuration term symbol = ⁷S

Am I correct?

[Corribus]

This is what I got as well. Now can you determine the rest of them?

[unsu]

if we allow the electrons to pair up, even on 4s orbital,
then there are 12 positions for 6 electrons, there must be 924 micro states 

if we can do whatever we want with d electrons but leave one electron on 4s orbital, then there are 2x256=504 micro states (2 because 4s and 4s  )

no pairing = 2⁶ = 64 microstates

plus different J values     

[Corribus]

if we can do whatever we want with d electrons but leave one electron on 4s orbital, then there are 2x256=504 micro states (2 because 4s and 4s  )

Well if you don't adhere to this restriction, then you're in another electron configuration, so...

I went through it quickly and (excluding J states) I found the following: ⁷S, ³I, ¹I, ³H, ¹H, ⁵G, ⁵F, ⁵D, ⁵P, 3x³G, 3x³F, 3x³D, 2x³P, 2x¹G, 4x¹D, ¹P.

I wonder if I'm right. Maybe we'll never know.