valence configuration

[nhakhanh]

Hi,
Does anyone know how to find the valence configuration for an element in group B (for example: group VB, group VIB,...).
Thanks and good luck to everyone

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[h20town08]

IVB, VB...they are in the d block:

1s
2s 2p
3s 3p 3d
4s 4p 4d 4f

s shell holds up to 2 electrons
p shell holds up to 6 electrons
d shell holds up to 10 electrons
f shell holds up to 14 electrons (you most likely won't see any this high)

According to Hund's rule, electrons occupy the orbitals of least energy first so you should go in this order when counting electrons: 1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, ...

for example Ti (22 electrons with a neutral charge) will have this config:
1s^2, 2s^2, 2p^6, 3s^2, 3p^6, 4s^2, 3d^2

add up the ^x(electrons) and it equals 22 and there you have your configuration. valence electron configuration would be 3d^2. When you get up to 3d^8 and 3d^9 the 4s electrons may jump to the higher orbital to reach the "octet rule" (3d^10). you probably won't see this for the purposes of the DAT though, but it is just a side note.

 

[jackbauer!]

the OP was asking about the valence configuration NOT electron configuration....there IS a difference.

the valance configuration generally includes those electrons in the s & p subshells of the highest principle quantum number, n, for a particular atom.

lets take Cr for example.

it's electron configuration is [Ar] 4s2 3d4
it's valence configuration is just 4s2 (hence Cr usually forms a 2+ ion to obtain the noble gas configuration as Ar)

hope this helps

jB!