Understanding Carbon Electrons: Is the Chemistry Book Right?

[leroyjenkens]

I was reading a chemistry book and found something that doesn't seem right to me.
Read the underlined part.
http://img139.imageshack.us/img139/6192/carbonz.jpg
Isn't that incorrect?
Doesn't it have two unpaired valence electrons instead of four?

 

[mccoy1]

I was reading a chemistry book and found something that doesn't seem right to me.
Read the underlined part.
http://img139.imageshack.us/img139/6192/carbonz.jpg
Isn't that incorrect?
Doesn't it have two unpaired valence electrons instead of four?

get a high school chemistry book and read it!

 

[leroyjenkens]

get a high school chemistry book and read it!

That's what I was doing until I reached this little obstacle.

 

[negitron]

I think you are unclear on the structure of electron orbitals and valences:

http://en.wikipedia.org/wiki/Atomic_orbital
http://en.wikipedia.org/wiki/Valence_electron

 

[Ygggdrasil]

If you are considering a carbon atom alone, you are absolutely correct. The 2s orbital has lower energy than the 2p orbitals, so the 2s orbital will contain two paried electrons and the 2p orbitals will contain two unpaired electrons.

However, when forming chemical bonds, carbon will generally hybridize its orbitals. The one 2s and three 2p orbitals will form 4 sp³ orbitals of equal energy. In this configuration, the four electrons will each go into separate orbitals.

 

[leroyjenkens]

I think you are unclear on the structure of electron orbitals and valences:

http://en.wikipedia.org/wiki/Atomic_orbital
http://en.wikipedia.org/wiki/Valence_electron

I thought I was clear enough, but I guess not. I was following along with this book from the start and I followed everything up to that point. They must have left a bunch of stuff out. That's pretty frustrating.
Anything specifically on those links that I should read that addresses this problem? Or is my way of thinking so upside down and backwards that I just need to read the whole thing?

If you are considering a carbon atom alone, you are absolutely correct. The 2s orbital has lower energy than the 2p orbitals, so the 2s orbital will contain two paried electrons and the 2p orbitals will contain two unpaired electrons.

However, when forming chemical bonds, carbon will generally hybridize its orbitals. The one 2s and three 2p orbitals will form 4 sp³ orbitals of equal energy. In this configuration, the four electrons will each go into separate orbitals.

Oh, this book doesn't explain all that.

It kinda just throws "variable valence" out there, too, without any explanation.

 

[pzona]

If you're reading this in a high school chemistry book (that's the highest level of chemistry I've studied by the way), just keep reading. You should come across the method with which electrons are distributed throughout the various orbitals very soon. If you haven't already, read ahead in the chapter and things should be a lot clearer.

I understand the problems you're having and it might take a few read-throughs to get it all. I'm not an expert by any means, but high school chemistry books (the ones I used anyway) are pretty good at explaining electron pairings and such.

 

[mccoy1]

That's what I was doing until I reached this little obstacle.

Okay let's see. First, you're correct by saying that carbon has 2 unpaired and two paired valence electrons.But remember that the carbon above is hybridised. For the formation of Hydrogen cyanide(HCN), carbon needs to make 4 bonds as usual, hence it has to provide 4 electrons . To do this, it promotes one of the 2s^2 electrons into an empty p orbital. Now it has 4 unpaired electrons(one for forming a bond with Hydrogen and 3 for forming 3 bonds with Nitrogen, Carbond contribute 3 electrons and N contributes 3).

I hope that help.