Question about bond lengths
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Question about bond lengths

[From: ] [author: ] [Date: 12-11-06] [Hit: ]
wikipedia.org/wiki/Electronega…-Thank you!Answers like yours make it fun for me to continue contributing.that would make me a genius right?Oh dear - I guess Ill have to keep on looking.Now dont you give up: no prize is worth having if its easily won.......
Take a look at this reaction w/bonds symbolized as -

H-H + F-F ---> H-F + H-F

(Imagine that there are the appropriate number of lone pair electrons around all the F's)

H-H bond length = 74pm
F-F bond length = 143pm
H-F bond length = 92pm

How come the HF bond length isn't simply the average of the H-H and F-F bond lengths?

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Did you stumble on this by yourself? If so, well done! It is the basis of Pauling's method of determining electronegativity (and Pauling won two Nobel prizes outright!). He attributed the difference to an ionic contribution to the H-F bond: δ+H-Fδ- and related the difference (geometric means rather than arithmetic means give better results) to the difference in electronegativity: χF- χH.
There is probably an MO argument but this should sufficient for you. peic
http://en.wikipedia.org/wiki/Electronega…

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Thank you! Answers like yours make it fun for me to continue contributing. "that would make me a genius right?" Oh dear - I guess I'll have to keep on looking. Now don't you give up: "no prize is worth having if its easily won." peic

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