# Electrons on outer ring (transition metals)

i know that if you want to figure out how many electrons an atom has on its outer ring (valence?), its 1 for group 1 (eg Na), 2 for group 2 (eg Mg), all the way to 7 for halogens and 8 for noble gases.

however, how do you figure it out for transition metals in the middle?

for example, Copper would have an electron configuration of

1s2 2s2 2p6 3s2 3p6 4s2 3d9

so would this have 2 because there is only 2 on its outside ring (n=4)? what about the 17 electrons in the 3 energy level?

is it possible for any atom to have more than 8 on its outside ring? what about the octet rule?

how do you use it to figure out its charge? again, groups 1 through 8 are reasonable and make sense since you add or subtract electrons to gain the octet. but what about transition metals again? how can you use the electron configuration to figure out what charge their atoms will be?

thanks.

anyone? help?

Gokul43201
Staff Emeritus
Gold Member
All the transition metals have 2 electrons in the valence shell (4s, 5s, or 6s), except for a few exception like Cr (and Mo) where it is energetically easier to have a half filled 4s (or 5s) subshell (only 1 electron), because this allows a half -filled 3d (or 4d) subshell. A similar argument works with with Cu, Ag, Au where the inner d subshell is fully filled.

The octet rule prevents an atom from having more than 8 valence electrons.

Yes it is possible for an atom to have more than 8 electrons. For the most part the octet rule is followed but now always!!Take phosphorus or sulfer for example. It is also possible for an atom to have less than 8. For atoms to have more than 8 electrons you must take sp^3d and sp^3d^2 hybridization into account. Basically you want to do what you can to have either no formal charge or the least amount of formal charge possible in the molecule.

Keep in mind that a transition metal does not lose electrons in the same matter as the other metals. They do not gain the configuration of the nearest noble gas. Also remember that transition metals generally have two oxidation states, that is for example they may lose either 2 or 3 electrons for iron. Electrons are generally lose from the s orbital first, however you have to take into account the configuration of the p orbital.....as sometimes those electrons may be lost first.

Does that help at all or is what I just said even more confusing?

Gokul43201
Staff Emeritus
Gold Member
scorpa said:
Yes it is possible for an atom to have more than 8 electrons. For the most part the octet rule is followed but now always!!Take phosphorus or sulfer for example.
P and S have respectively 5 and 6 valence electrons; so I don't understand what you're saying here.

Gokul43201
Staff Emeritus
Gold Member
Didn't notice this before, but this is wrong :
dnt said:
for example, Copper would have an electron configuration of
1s2 2s2 2p6 3s2 3p6 4s2 3d9
As I mentioned in my earler post, Cu is one of the transition metals with an unusual configuration - it should be 4s1 3d10. This is why copper (unlike most other transition metals) has a +1 oxidation state (cuprous(I)).

Gokul43201 said:
P and S have respectively 5 and 6 valence electrons; so I don't understand what you're saying here.

Yes that is true, but the orbitals can hybridize resulting in an expanded valence orbital. For example phosphorus undergoes sp3d hybridization allwing it to form bonds with its 5 electrons, resulting in it having 10 electrons when bonded instead of 8 (it would bond to 5 chlorine atoms for example). Without hybridization this would not happen as you would have lone pairs which would not experience bonding. Sulfer goes through sp3d2 hybridization resulting in it having 12 electrons when it is bonded. I don't know if that makes any more sense, I am horrible at explaining things over the computer.

Oh wait I think I get the problem!

It is not possible for an atom to have more than 8 valence electrons if it is alone and has nothing bonded to it.

It is possible for an atom to have more than 8 valence electrons if it is bonded to other atoms forming a molecule for example PCl5.