I just need a definitive answer because I've searched everywhere and it's made me second guess my original answer.
How many valence electrons does copper have? I thought it was one but now I'm unsure. I know it's electron configuration is [Ar]4s1 3d10, so that's why I said it was one but then it got marked wrong so is 11 right? 2? I have no idea.
Frankly, I think the whole idea of valence electrons with transition metals is nonsense unless the rules make sense and most don't. I've spent almost two hours looking at page after page for an explanation of valence electrons. No two sites give the same rules for transition metals (Cu is a transition metal). The rules are straightforward for groups 1,2,14-18 but not for groups 3-12.
Here is the best site I found but it doesn't agree with other sites about how to treat groups 3-12.
http://www.wikihow.com/Find-Valence-Electrons
I define valence electrons as those in the outside shell. For Cu that is 1 because of the electron configuration which you have correct. And almost all sites agree you don't count FILLED 3d orbitals (which is the case with Cu), then they do count them on groups 3-12. If your key is counting that +1 wrong the author of the key is not defining it the same way. I can understand why 2 might be permissible BUT that isn't the electron configuration ALTHOUGH +1 AND +2 are possible oxidation states. On that basis, the number of valence electrons is +2 for Mn ALTHOUGH it has common oxidation states of +2, +4 and +7 with some others thrown in for good measure. Having said all of that, I think +1 should be the answer; and no, 11 is not right.
I think the confusion is caused by the general idea that most of us have about using the words oxidation state and valence interchangeably and not having set rules about when we count and when we don't count electrons in inner orbitals. Hope this helps and doesn't confuse.
That's very helpful! Thank you!
No problem! Let's go through the process of determining the number of valence electrons for copper together.
To find the number of valence electrons, we need to look at the outermost electron shell, which is the highest energy level. In the case of copper (Cu), its electron configuration is [Ar]4s1 3d10.
The first part, [Ar], represents the electronic configuration of the noble gas argon. Argon has a full electron configuration of 1s2 2s2 2p6 3s2 3p6.
The next part, 4s1, tells us that there is one electron in the 4s orbital.
Finally, 3d10 indicates that there are ten electrons in the 3d orbital.
To determine the number of valence electrons, we only consider the outermost shell, which is the 4s orbital for copper. Therefore, copper has one valence electron.
So, your original answer that copper has one valence electron is correct. However, it's essential to note that copper can have different oxidation states, which means it can lose or share different numbers of electrons in chemical reactions. This is why copper can exhibit various oxidation states despite having only one valence electron.
I hope this explanation clears up your confusion!