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Electronegativity & Bonds

by RobinSky
Tags: bonds, electronegativity
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RobinSky
#1
Dec5-11, 04:33 AM
P: 112
I recently found a table of electronegativity differences, where certain differences where used to define certain types of bonds. However I found different values at different sites so I wonder if someone could help sort this out.

Link 1

http://www.files.chem.vt.edu/RVGS/AC...ctronegativity

This is the values I used for comparing the bonds witihin the molecules but had to stop when I found new ones. Also found another one saying an electronnegativity difference of less than 0.4 (instead of 0.5) is nonpolar covalent bonds...

Link 2

http://www.mikeblaber.org/oldwine/ch...ity/Bond05.htm

This one is the most wierdet making huge value differences compared to what I have found more.

Link 3

http://www.chemteam.info/Bonding/Ele...-Polarity.html

This one brought up new unmentioned "rules"

However further research with this just didnt make any sense.

Sodium sulfide, lets take the sulfide ion, they say that the S-O bond is COVALENT, HOW? The electronneg. diff. gives you 3.5-2.5=1 which is LARGER than 0.4(or 0.5 who ever is correct). How can this be a NONPOLAR covalent bond, I am just confused...

What is the correct values for electronnegativity?

Thanks in advance
Regards, Robin Andersson.
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dextercioby
#2
Dec5-11, 07:46 AM
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The limit is 1.7-2 depending on sources. So if the electronegativity difference between the atoms is less or equal to 2, then the bond is rather covalent, except for metal ions (rule 4 in 3rd link). Whether the bond is polar/non-polar, the threshold is then 0.4/0.5. Where did you find that S-O bond is non-polar ? (SO or SO_2, the bonds are covalent and with hybridized orbitals).
RobinSky
#3
Dec5-11, 03:03 PM
P: 112
Quote Quote by dextercioby View Post
The limit is 1.7-2 depending on sources. So if the electronegativity difference between the atoms is less or equal to 2, then the bond is rather covalent, except for metal ions (rule 4 in 3rd link). Whether the bond is polar/non-polar, the threshold is then 0.4/0.5.
I see, thanks a lot!


Quote Quote by dextercioby View Post
Where did you find that S-O bond is non-polar ? (SO or SO_2, the bonds are covalent and with hybridized orbitals).
I'm having troubles finding the URL again but it was from a reply from someone (at answers.yahoo) while I was googling around on covalent, sulfide, oxygen and such.

So the S-O bond is a polar-covalent bond as I first suspected? And not a non-polar covalent bond?

"2. If the ΔEN is between 0.5 and 1.6, the bond is considered polar covalent"
S-O ΔEN is 1.0.

Thanks for the reply, it is really appreciated because I'm trying to solve out any of the left over riddles now before my preliminary examination next week in this chemistry course.

dextercioby
#4
Dec5-11, 05:22 PM
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Electronegativity & Bonds

SO_2 has a dipole moment, it's a polar molecule according to the general rule, as well as according to <Inorganic Chemistry> by J.E. House, page 345. (Elsevier, 2008).
Borek
#5
Dec6-11, 01:49 AM
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Please note that bond classification (ionic vs covalent) is not too precise, and that electronegativity difference is just a rule of thumb. So you deal with two approximate concepts, no wonder there are some gray areas.
RobinSky
#6
Dec6-11, 01:47 PM
P: 112
Thanks guys! I also had the chance to talk to a phd student in organic chemistry today so I really got this now. Seems like the first source I read regarding the S-O bond was wrong then, thanks! :)


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