Talk:Covalent bond

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[edit] '03 - '04 comments

"Atoms tend to share electrons in such a way that their outer electron shells are filled." Isn't that misleading, given that the stable number of 8 electrons is not the maximum number of electrons that can fit in the third shell and beyond?

No, see electron counting.

I just have a question, maybe you all can help me!..What is an example of a Covalent Bond and explain what is happening at the atomic level during bonding?.... im doing a chemisrty paper and that is one of the questions, if you know the answer.. please tell mee!

Ahem...the picture seems to show a CH4 molecule but says "ethene". Don't want to mess with the picture (I'm not great at graphics) but would some other Most Honorable Wikipedian care to look after it? Kosebamse 09:55 Mar 23, 2003 (UTC)

Covalent bonds are more common between non-metals, whereas ionic bonding is more common between two metal atoms or a metal and a non-metal atom.

What would be an example of an ionic bond between two metal atoms? This would require that a metal form an anion. Josh Cherry 22:24, 17 Oct 2003 (UTC)

Yep - I've corrected it.... --Ian 09:34, 29 Jan 2005 (UTC)

== Cis and trans ==
Straight- or normal-chain (even-numbered), monoenoic components, i.e. with one double bond, make up a high proportion of the total fatty acids in most natural lipids. Normally the double bond is of the cis- or Z-configuration, although some fatty acids with trans- or E-double bonds are known.

This seems completely out of place to me. I'm tempted to remove it. Josh Cherry 22:31, 17 Oct 2003 (UTC)

I encourage you to indulge yourself, but I do think it would be nice to keep a linked mention of cis and trans in there somehow, because people encounter these terms all the time now with "trans fats" in the news, and so I think even somebody who is just at the stage of learning what a bond is would do well to have the difference between cis and trans included in their curiculum. Most people won't want to go on and delve into an article about IUPAC naming rules or about alkenes, and yet they're liable to encounter "trans fat" and "trans double bond" and wish they knew what it meant. The stuff about lipids belongs in an article about lipids or fats, I think. 168... 00:10, 18 Oct 2003 (UTC)
I've just axed it. This article is about covalent bonding, and that was talking very specifically about the bonding in fatty acids. cis and trans is something much more general than that, I don't think that the description there helped much. Iridium77 13:38, 22 May 2004 (UTC)

I don't know why this article says that covalent bonding is STRONGER than ionic bonding? This is incorrect... Unless Im mistaken

Covalent bonding is usually stronger than ionic bonding. Iridium77 13:39, 22 May 2004 (UTC)

[edit] Electron Dot Notation

Does anyone have plans for an Electron Dot Notation article? A seperate, improved article would be useful. It would need step by step instructions, ect. Alternatively, someone could link the Electron Dot Notation page to this one, but that would be slightly inadequate I'd do it myself, but I'm laking in time and skill. Pingveno 04:46, 1 Dec 2003 (UTC)

Such "step by step instructions" is more suitable at wikibooks:. --Menchi 04:58, 1 Dec 2003 (UTC)
Does much of anything even exist there? If so, then just link there. Pingveno 05:09, 1 Dec 2003 (UTC)

Also noticed that a page concerning the naming of covalent compounds, and indeed any naming conventions for all of Chemistry, would be extremely useful. Pingveno 05:24, 1 Dec 2003 (UTC)

[edit] Covalent radius

Covalent radius is made a redirect here, but this page does not contain the word "radius". Probably covalent radius should be made into real article, like they have it on other wikipedias: de:Kovalenter Radius, fr:Rayon de covalence and pl:Promień walencyjny, to name a few. --romanm (talk) 21:51, 28 Sep 2004 (UTC)

Nobody complaint, so I at least made a stub instead of redirect. Please see covalent radius and try to improve it. --romanm (talk) 13:49, 17 Oct 2004 (UTC)

[edit] Left, right, and up

The three shared orbitals in a triple bond can be imaged as left, right, and up.

I don't see what this is trying to convey. The two pi bonds are at right angles to each other, looking down the bond axis, and the sigma bond is symmetric about the axis, or straight ahead if you like. Where does "left, right, and up" come from? Which one is the sigma bond? Josh Cherry 03:55, 5 Oct 2004 (UTC)

A correct way to say this would be middle, up and down and left and right, π bonds are "surronding" the σ bond at a straight angle. Orbital hybridisation is one theory that explains this.
A quadruple bond as in C2 would be a σ-bond and three π-bonds. The σ-bond forms directly between the two carbon atoms, but is shunted upwards by the repulsive force of the two π-bonds to the left and right (hence left, right and up). The third π-bond would have to bend all these bonds excessively, leading to instability. I am, however, working on an A-level view of how bonds form, so please correct me if I'm wrong. Thomas Winwood 23:04, 15 Dec 2004 (UTC)
I don't doubt that there would be a steric issue with a fourth bond, but I still don't see the "left, right, and up" in a triple bond. The two π-bonds are at right angles to each other, so "left" and "right" doesn't make sense to me. I don't understand in what sense the σ-bond is "shunted upwards" either; if it's direction is to be called "up" in a triple bond, it's "up" in a single or double bond too. Josh Cherry 23:40, 15 Dec 2004 (UTC)
I really think the reference to a quadruple bond for C2 and Si2 is mistaken, so we should remove it all. C2 is normally described as having a double or maybe triple bond - it isn't explosive, merely unstable. Quadruple and higher bonds get described for esoteric transition metal compounds, but that's it. So, unless someone has good reference sources to show otherwise, I'll chop it soon!--Ian 14:02, 8 Feb 2005 (UTC)

[edit] Rotation of double/triple bonds

I thought that this was relavant to this article, so I put a couple of sentences in on it. I wanted to make sure with someone else on this before I put it in though: Is a triple bond less rigid than a double bond in terms of rotation? I would think so because in a triple bond, the pi orbitals being used are perp. to each other, so when you rotate it, then there will be at least some orbital overlap. Compare that to a double bond where when you rotate it 90 degrees, then there is no pi overlap at all. That's what I seem to remember from gen chem, but I can't find any notes on it or any external refs either.Sareen eng 06:43, 28 July 2005 (UTC)

Um-- The diagram is BAD considering quantum mechanics. The Bohr model of the atom is dead.

[edit] Giant macromolecular covalent vs simple covalent molecular

Shouldn't this be mentioned somewhere? EvilStorm 15:39, 19 January 2006 (UTC)


[edit] The bond order section

Hi,

I'm confused... I just studied from the Books of Pettifor and Suttun. And they seem to define bond order as something very different, thatn what is the article.

In those books, bond order is half the difference of the nuber of electrons in the bonding and those in the antibonding state. Example: A bond order of 1 means: Two electrons in the bonding and none in the antibonding state.

Wether the bond is sigma or pi doesn't have anything to do with bond order, but is determined by the angular momentum across the bond axis.

Could someone make the connection, please?

Mouvement 14:51, 9 April 2006 (UTC)

This usually yields the same result. Think about it. --Spoon! 21:58, 29 August 2006 (UTC)

Bond order as defined currently is usefully general; when defined as the difference between bonding and antibonding electrons it is specific to simple molecular orbital theory. And as written, the mention of sigma and pi bonds is correct, and fits with high school ideas.Ian 08:41, 30 July 2007 (UTC)

[edit] Stronger than an ionic bond?

I've learned that ionic bonds are stronger than covalent bonds, since the ions have a greater amount of attraction between them. Can the person who stated that covalent bonds are stronger cite their sources? 67.172.180.215 05:30, 19 July 2006 (UTC)

Sources are probaly their teachers instead of qualified scientists. The problem comes with the fact that there is no real line bewtween covalent and ionic bonding (there is a formal defination but thats just to make it easier to communicate). Also, how do you define bond strength and what two substances would you compare?

[edit] Polarity in ozone

Hi! I think ozone is a bad, or better, a too difficult, example, polarity in that molecule is for a different reason than electrons not being 'shared equally'. Ozone has two resonance structures. But either do not exist, the electrons are equally shared between the bonds (Lewis structures are only a model). The polarity in this molecule is more the result of the molecule not being linear, but bent. --Dirk Beetstra T C 22:44, 29 August 2006 (UTC)

Okay, I was the one who put that there. I will retract it and talk about the polarity of ozone in chemical polarity. --Spoon! 08:32, 31 August 2006 (UTC)
Maybe the C–C bond 1,1,1-trifluoroethane is a cleaner example? Due to the high electronegativty of F, C1 would be quite δ+, whereas C2 would not be. But by adding partial charges, one could argue that the effective electronegativity of the carbon atoms has changed. Semi-equivalently, one could consider that the bond is really between "the carbon on a methyl group" and "the carbon on a trifluoromethyl group", not just between two carbons, so the electronegativity difference of the group is what matters, not just the specific bonded atoms. DMacks 12:52, 31 August 2006 (UTC)

[edit] unhelpful definition

as a student that is studying chemistry, i dont think the definition of the covalent bond is defined clearly.Missy1234 23:47, 17 January 2007 (UTC)

True.

Not to mention, it could be further defined into polar covalent and apolar covalent bonds, which although are redirected to this article, are in fact not discussed.

I would personally like to add a section on Lewis structures (aka. electron dot diagrams), polar and apolar covalent bonds, and co-ordinate covalent bonds.

However, most of my resources belong to the University of Technology, Sydney, Australia. Thus, the resources are unavailable to the public.

[edit] Unsaturated bond

The page for unsaturated bond redirects here.. but this page does not say anything about unsaturated bond. maybe to chemistry students, this might be obvious, but as a public encyclopedia it should be clear exactly how this page relates to an unsaturated bond. as it is this page gives me no information and I am left completely in the dark as to what a unsaturated bond is. Drag-5 (talk) 18:41, 19 November 2007 (UTC)

That does seem not-very-useful. I just re-redirected Unsaturated bond to Unsaturated compound. DMacks (talk) 19:05, 19 November 2007 (UTC)

[edit] Article Needs Help, Bad First Picture

Sorry, but this article strikes me as rather poorly written, and, sorry again, I am not the guy to make the corrections. I hope someone more qualified agrees and takes the necessary steps. But that first picture!!--what a useless piece that is! Does ANYONE know what it means? If so, please give it a better description, or fix it. I am not clueless about chemistry, but I felt like I was, looking at that picture! What do those dashed lines and non-dashed lines mean? And what is the significance of the angles? And, okay, so those arrows are electrons, but...what do they mean??? You got three going one way and one going the other way... --Taquito1 (talk) 02:37, 10 February 2008 (UTC)

That's actually a simplified molecular orbital diagram, and I must say it's actually quite well drawn. --Rifleman 82 (talk)
Actually, the energy gap for the right image should be smaller, since there is poorer size and symmetry overlap between both participating atomic orbitals (as defined by polar covalent). All things being equal, of course. --Rifleman 82 (talk) 03:23, 10 February 2008 (UTC)

[edit] Text and Pic don't match

In the para before you present the Lewis diagram, the text says:-

"Some examples of Electron Dot Notation are shown in the following figure. An alternative form, in which bond-forming electron pairs are represented as solid lines, is shown alongside."

Well I've two problems with that:

1. There's only one figure so it should say "An example" not "Some examples"

2. The 2nd sentence says "An alternative form... ..is shown alongside" - But it ISN'T!

I do wish someone who understands organic chemistry would clean this up, because I'd like to understand the solid line figures better. Edetic (talk) 10:06, 27 April 2008 (UTC)