DeusExMachina
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Understanding Covalent Bonds
Okay, Darkfire is helping me with learning chemistry through e-mail, AIM and MSN Messenger. He hasn't been on for a while and he had just started
to talk to me about covalent bonds. I know that they are very important so maybe someone can tell me how they work here (or maybe Darkfire will see
this post and go online). So... any help with this?
Oh, and I am still searching on Google for covalent bonds. I also know that a covalent bond is when one or more electron is shared between two atoms
to make a bond (I think so...).
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Beanspike
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Hello Deus
I think I may be able to shed some light on this.
"A covalent bond is one in which two atoms share a pair of electrons. Let us examine a typical case, that of the element flourine. Each
flourine atom has seven outer-shell electrons and needs one more to complete the octet. Of course, the flourine atom could gain an electron and
thereby become a F- ion, but it can only do this if there is a nearby atom (or molecule) from which to take the electron. It cannot get an electron
from nowhere. If we have a sample that contains only flourine atoms, then the only nearby atom would be a flourine atom.Would a flourine atom take an
electron from another fluorine atom? A little thought shows that the answer is no. The first atom would be a stable F- ion, with a complete outer
shell, but the second would be a very unstable F+ ion with only 6 outer-shell electrons. Fluorine atoms instead share an electron to form covalent
bonds. When they do this, both atoms have a complete octect."
F(7e) + F(7e) ---->F2
Introduction to General, Organic, and Biochemistry (5th edition)
[Edited on 17-4-2003 by Beanspike]
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Madog
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in reality there is no pure ionic bond or coavelent bond, theyre are just bonds that are more coavelent and ones that are more ionic
Most people outgrow their pyro tendencies, we are the ones who\'s tendencies outgrew us.
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DeusExMachina
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what do you mean by that?
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DDTea
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I will do my best to explain this very clearly...but this is difficult when I am unable to draw dot-stuctures to help understand.
A general definition of a covalent bond is where atoms share electrons to fill their outer electron shell. There are four types of Covalent bonds-
Single Bonds, Double Bonds, Triple Bonds, and Coordinate Covalent Bonds.
In a single bond, each atom contributes just one electron to the bond. An example of this is with the Halogens, where each atom has 7 valence
electrons and needs one more. So, they bond with each other, and each contributes one electron to the other's shell, making something like this:
Cl : Cl The top dot of that colon belongs to the left Chlorine, while the other dot belons t othe right Chlorine. Of course, on the other 3 sides
of each Chlorine, there are also dots...but I could not draw them, and they are not involved in the bond =).
In a double bond, each atom contributes Two Electrons to the bond. An example of this is in Ethene, whose dot structure would be drawn like this (of
with dots on each side of the Carbons, of course...)
(H2):C::C H2) Don't pay much attention to the two Hydrogens bonded to each
Carbon, because they are not what i'm trying to stress.
As you would guess, in a triple bond, each atom in the bond contributes 3 bonds to the bond! This is drawn similarly to the double bond, but uses 3
layers of dots instead of just 2. Examples of this are in Diatomic Nitrogen and in Acetylene.
Coordinate Covalent bonds are the weird ones, but not too weird  . This is when
just one atom contributes TWO electrons to a bond, while the other atom contributes nothing. A good example of this is in the Chlorate Ion, ClO4.
This would be drawn as follows, only with Oxygens on each side of the Chlorine...
X-O-Cl: O . Let me explain this... the X represents a metal or whatever bonded to the Chlorate ion. The two lines represent single-bonds, for now.
The Colon represents the Coordinate Covalent bond... the Chlorine is providing two electrons from its valence electron shell, while Oxygen is
providing nothing...just making use of said two valence Chlorine electrons.
[Edited on 4-18-03 by Samosa]
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Darkfire
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Oh i think you meant ethene instead of that first aceteline.
CTR
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Mumbles
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Bonding is just bonding. Ionic and covalent are just measures of how strong the polarity is. It works out that metals are too different from non
metals to form covalent bonds, I think. Correct me if I'm wrong. Metals also have an designated oxidation state(s)
Ionic > 2.0
Polar Covalent > or = .4 but < or = 2.0
Non Polar Covalent < .4
Those are electronegitivity values. Its on a bond by bond basis. The only exception to this is when the polar bonds of a molecule are symetrical.
For example CO<sub>2</sub> is non polar, even though it has 2 polar bonds.
<c>O=C=O
- + -
<-- --></c>
I know its a bad drawing, but the C and O bond has a delta EN value of 1.0, therefore being polar. However since theres another one on the other side
they cancel each other out, overall being nonpolar.
On a completely different noI wrote out a rather complete explanation of covalent bonding, but when I went to submit it the webpage couldn't be
reached. I was very perturbed.
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DeusExMachina
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Darkfire isn't on right now so I'll post this here (madscientist said it was right)
N has a valence of 5. To complete the ocet, the two N atoms will have to make one triple bond each and share electrons to finish the outer shell (8
outer electrons). Or, when N makes a bond with another tpye of atom, it and the other atom will have to make several double or single bonds to
complete the ocet and make a bond between the two of them.
Darkfire told me that N would have to make double or single bonds and not triple bonds if it was bonding with another atom other than N.
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Darkfire
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Oops, sorry i meant to say something diferent, acualy in bond to ther elements N can make up to 3 bonds, well really even 5, see science has so many
exeptions it makes teaching very hard. Really because of its size N shouldnt be able to expand its octet, but in some case it does.
\"I love being alive and will be the best man I possibly can. I will take love wherever I find it and offer it to everyone who will take it. I
will seek knowledge from those wiser and teach those who wish to learn from me.\" Duane Allman
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DeusExMachina
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when N bonds with H, there has to be three H atoms to bond with N because H can only make one bond and N's valency
is 5. So if three Hs give one bond each, the ocet for N can be completed and all the atoms can be bonded together...
It would be something like this:
H-N-H
\
H
the line below N should be straight but I couldn't figure out how to do that... I think I'm starting to get this but I know I'm missing
some major stuff
that I need to know. I really don't know what I need to know next. I guess Darkfire knows what's next but I guess you guys can give
suggestions for that too (I'm still learning covalent bonds so it has to be something with that)
Oh, and if I understood right from what darkfire told me, the reason N is N2 is that when N bonds with N, each N has to make a triple bond so there
will be
twi electrons left on the ocet. I don't think I did understand it right though.
[Edited on 22-4-2003 by DeusExMachina]
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