Understanding Lone Pairs & Orbitals

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Main Question or Discussion Point

So, trying to understand conceptually why Carbon can only have 4 bonds maximum, regardless of its formal change in a structure. My book says it's because it only has 4 orbitals, but I'm not quite sure why this is, and was wondering if someone could explain.

My second question is regarding lone pairs. A typical Oxygen atom with 6 Valence would have 2 lone pairs and 2 unpaired electrons. My book says this means it can form two bonds, but my question is, why can it not make bonds through its lone pairs (could it make double bonds if it finds another atom with a lone pair?).

Thank you for any help.
 

Answers and Replies

  • #2
Wax
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So, trying to understand conceptually why Carbon can only have 4 bonds maximum, regardless of its formal change in a structure. My book says it's because it only has 4 orbitals, but I'm not quite sure why this is, and was wondering if someone could explain.

My second question is regarding lone pairs. A typical Oxygen atom with 6 Valence would have 2 lone pairs and 2 unpaired electrons. My book says this means it can form two bonds, but my question is, why can it not make bonds through its lone pairs (could it make double bonds if it finds another atom with a lone pair?).

Thank you for any help.
Books like to confuse you a lot but it would have helped if you said what subject you were studying general chemistry or organic chemistry. Have you heard of the octet rule? It's the rule that says all atoms want to be stable with with a total of eight electrons. This rule generally applies to organic chemistry, in general chemistry there will be compounds that have more then an octet.

Anyway, carbon from the periodic table only has 4 elections. Therefore, you will need 4 more elections to it to be satisfied. The same thing goes for Oxygen. Oxygen has 6 elections and needs a total of 8 to be satisfied, so it will need two more elections.
 
  • #3
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I'm studying Organic Chemistry. All atoms want 8 valence electrons? I'm still not getting your answers to the question though. Why 4 orbitals, what does that mean? Also do you know the second part of my question?

Thanks.
 
  • #4
Wax
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Do you have an exam coming up? I'm assuming this is your first exam? It looks like you are asking a lot of questions in one night. LOL

Okay, first off you are making everything too complicated. What your text is trying to tell you is that Carbon will always have eight elections. If it doesn't have eight then it will make eight when it connects to any other atom. Remember that picture you drew in your other question? Try and count how many elections are in each carbon atom.
 
  • #5
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Thanks for the reply.

Heh, no, no exam coming up, just doing some studying. I understand about the valence electrons, but I still am unsure about my two main questions:

1) What is meant by four orbitals? Merely 8 electrons, two in each orbital? What are these orbitals?

2) Why can't lone pairs be used in bonds? Can they be used to form double-bonds with another lone pair?
 
  • #6
Wax
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Thanks for the reply.

Heh, no, no exam coming up, just doing some studying. I understand about the valence electrons, but I still am unsure about my two main questions:

1) What is meant by four orbitals? Merely 8 electrons, two in each orbital? What are these orbitals?


2) Why can't lone pairs be used in bonds? Can they be used to form double-bonds with another lone pair?
1) Are you reading the section about pie bonds and orbitals? If you are then just memorize what your professor said in the notes. It's nothing there to really understand.


2)A bond is two elections, lone pairs are bonds... :rofl:
In about 2 or 3 weeks time you will see that lone pairs can be broken up to form all kinds of bonds. I think you are thinking about this too much.
 
  • #7
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Thanks for the reply.

1) Actually I don't have a teacher right now, just learning from a textbook. Still wondering about the 4 orbitals, and what they are called, etc. But I suppose I can leave that question for now.

2) Right, I guess I see how a lone pair is a bond, which is why I was asking if you could form a double bond with two atoms, each with a lone pair. If you view a single bond as this:
C . . C, couldn't you have this C::C?
 
  • #8
Wax
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Thanks for the reply.

1) Actually I don't have a teacher right now, just learning from a textbook. Still wondering about the 4 orbitals, and what they are called, etc. But I suppose I can leave that question for now.


2) Right, I guess I see how a lone pair is a bond, which is why I was asking if you could form a double bond with two atoms, each with a lone pair. If you view a single bond as this:
C . . C, couldn't you have this C::C?

1) Learning organic chemistry for fun? heh.. Anyway, if you are reading that section that I think you are reading then just remember it's all theory. What I mean is that, most professors don't understand it themselves because it is a relatively new concept. On an exam, it's just 3 or 4 things you have to remember about pi bonds and orbitals.


2)What your book is trying to do is, help you understand the concept of drawing structures. Try looking at example question from that section to see what it is your book wants you to understand instead of reading too much in between the lines. As for your question, you can form single, double, and triple bonds. On and exam you will be required to draw that reaction. In a reaction, single electrons will always form bonds first. Double bonds will be the next best thing to react if there are no lonely elections.

Lone pairs aren't really bonds, they are just satisfied. Two electrons are happy. That's the most important thing. I just said they were bonds earlier to help you understand that they are satisfied.
 
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  • #9
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1) More like studying in preparation of getting destroyed come Fall. Thanks though, I'll just keep reading about it.

2) Okay, thank you.
 
  • #10
Wax
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Read the section to get the general knowledge, then open the end of the chapter and work the problems. That stuff is on the exam.
 
  • #11
Borek
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1) What is meant by four orbitals? Merely 8 electrons, two in each orbital? What are these orbitals?
One s orbital (2s to be precise) and three p orbitals (2px, 2py, 2pz). If you have just opened your eyes and mouth wide, you should get back to GenChem101 quantum chemistry intro.
 
  • #13
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One s orbital (2s to be precise) and three p orbitals (2px, 2py, 2pz). If you have just opened your eyes and mouth wide, you should get back to GenChem101 quantum chemistry intro.
Do you know any place where I can read more about that? I'd love to actually understand it.

Thanks.
 
  • #14
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Those orbitals combine to make four hybrid sp3 orbitals. Observations show that carbon never makes more than 4 bonds and to rationalize the tetrahedral geometry as seen by a molecule like methane. http://en.wikipedia.org/wiki/Orbital_hybridisation
 
  • #16
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High School Chemistry 101- If you're interested...

Orbitals= the likely location of an electron in an atom... kind of like if you pluck the guitar string and you see the blur of vibration and you know the string is (likely to be) somewhere in that blur... its all probabilities when it comes to electrons, Heisenburg's Uncertainty Principal and all that.

So...

Within each atom is a bunch of electrons, each in their own energy level (you can imagine it as a series of concentric circles around a nucleus) and The circle closest to the nucleus is the first and lowest energy level, the next biggest circle is the second energy level, and so on. On each energy level are sublevels, named s,p,d,f,g,h, etc.... You can illustrate these as little dots on the circles. Within each sublevel are an odd number of orbitals, each orbital containing up to two electrons.

The way its all set up looks like this:
http://myimages.bravenet.com/136/355/834/1/atom.png [Broken]

The first energy level has a s sublevel, which has one orbital (one red dot containing up to two electrons). This first energy level can only hold a max of two electrons. The second energy level has a s sublevel (with one [red] orbital containing up to two electrons) , and a p sublevel, which has three [yellow] orbitals, each orbital containing up to two electrons. The second energy level therefore can hold a max of eight electrons. The third energy level has an s sublevel (one red orbital), a p sublevel (three yellow orbitals) and a d sublevel with five green orbitals. The third energy level can hold a max of eighteen electrons. It goes on from there, each successive energy level having all of the sublevels of the lower energy level plus one more. Each sublevel has two more orbitals than the previous one.

So, as you may have guessed, an atom doesn't actually look like this, but to draw the actual shape of the orbitals would be too difficult for my meager artistic skills... to confuse you more, I'll tell you that an s orbital is a sphere around the nucleus and that the difference between an s orbital on the first energy level and an s orbital on the second energy level is that the second energy level s orbital has a larger diameter than the s orbital on the first energy level.

Meh. The website does a better job of explaining it.
 
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  • #17
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Chemistry 101- If you're interested...

Orbitals= the likely location of an electron in an atom... kind of like if you pluck the guitar string and you see the blur of vibration and you know the string is (likely to be) somewhere in that blur... its all probabilities when it comes to electrons, Heisenburg's Uncertainty Principal and all that.

So...

Within each atom is a bunch of electrons, each in their own energy level (you can imagine it as a series of concentric circles around a nucleus) and The circle closest to the nucleus is the first and lowest energy level, the next biggest circle is the second energy level, and so on. On each energy level are sublevels, named s,p,d,f,g,h, etc.... You can illustrate these as little dashes on the circles. Within each sublevel are an odd number of orbitals, each orbital containing up to two electrons.

The way its all set up looks like this:
http://myimages.bravenet.com/136/355/834/1/atom.png [Broken]

The first energy level has only an s sublevel, which has one orbital (one red dash), the second energy level has a s sublevel (one red orbital), and a p sublevel, which has three (yellow) orbitals, the third energy level has an s sublevel (one red orbital), a p sublevel (three yellow orbitals) and a d sublevel with five (green) orbitals and it goes from there, each successive energy level having all of the orbitals of the lower energy level plus one more sublevel. Each sublevel has two more orbitals than the previous one.

An atom doesn't actually look like this, but to draw the actual shape of the orbitals would be too difficult for my meager artistic skills... to confuse you more, I'll tell you that an s orbital is a sphere around the nucleus... the difference between an s orbital on the first energy level and an s orbital on the second energy level is that the second energy level s orbital has a larger diameter than the s orbital on the first energy level.


...and that is all I know about orbitals an the atomic model.
 
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  • #18
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Does a 2s orbital cover the area of the 1s orbital as well?
 
  • #19
Borek
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Yes. All orbitals use the same space and they all to some extent overlap.
 

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