Bond Lengths

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Madelyn Cearlock
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Joined: Fri Sep 28, 2018 12:19 am

Bond Lengths

Postby Madelyn Cearlock » Mon Nov 19, 2018 1:41 pm

Can someone explain how to determine the bond lengths given that the single bond length is 140pm and the double bond is 120pm in a nitrate structure?

Carissa Young 1K
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Joined: Fri Sep 28, 2018 12:17 am

Re: Bond Lengths

Postby Carissa Young 1K » Mon Nov 19, 2018 1:55 pm

First, realize that nitrate's lewis structure has resonance and is the reason why the bond lengths are averaged. This blend of single and double bond lengths accounts for this averaged length.

vaishali 1D
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Joined: Fri Sep 28, 2018 12:19 am

Re: Bond Lengths

Postby vaishali 1D » Wed Nov 21, 2018 4:27 pm

Because there is resonance, you can average the two. The average of 140 and 120 is 130, therefore the bond length should be 130 rpm

Stevin1H
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Joined: Fri Sep 28, 2018 12:17 am

Re: Bond Lengths

Postby Stevin1H » Thu Nov 22, 2018 12:52 pm

Since the structure of nitrate has both a double and single bond, we have to understand that their is resonance involved. Also, remember that double bonds have shorter bond lengths than single bonds because double bonds are stronger. Resonance affects the strength of bonds because it spreads multiple-bond character over the bonds between atoms so single bonds are strengthened while double bonds become weaker as a result of the bond lengths being averaged.

Vicky Lu 1L
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Joined: Fri Sep 28, 2018 12:18 am

Re: Bond Lengths

Postby Vicky Lu 1L » Sat Nov 24, 2018 12:53 am

Due to resonance, the most stable structure of the nitrate will be an average of the bonds nitrate holds which is both a single and double bond. As an overall molecule, nitrate's structure will even out and be an inbetween version of a single and double bond. Therefore, the average of 120 and 140 is 130.

Jasmine Chow 1F
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Re: Bond Lengths

Postby Jasmine Chow 1F » Sat Nov 24, 2018 1:14 am

There is resonance therefore, you take the average of the two.

Tony Chung 2I
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Joined: Fri Sep 28, 2018 12:19 am

Re: Bond Lengths

Postby Tony Chung 2I » Sun Nov 25, 2018 5:26 pm

You can take the average of the two

Anna O 2C
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Re: Bond Lengths

Postby Anna O 2C » Sun Nov 25, 2018 5:50 pm

If a structure has multiple bonds then the total molecule will have bonds the average length of all the present bonds. A molecule that has resonance has multiple possible bond placements in a Lewis structure, but this simply translates to having bonds that are averaged out over the different bond lengths. If you have a 120pm and a 140pm set of bonds in a molecule, the electrons will be held an average of those lengths or somewhere around 130pm.

Michelle Nwufo 2G
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Joined: Fri May 18, 2018 3:00 am

Re: Bond Lengths

Postby Michelle Nwufo 2G » Sun Nov 25, 2018 10:14 pm

So resonance creates a more stable bond, but how do lone pairs affect the strength of the bonds within a molecule?

Sapna Ramappa 1J
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Joined: Fri Sep 28, 2018 12:24 am

Re: Bond Lengths

Postby Sapna Ramappa 1J » Mon Nov 26, 2018 5:55 pm

Because there is resonance here, the bond length is the average of the bond lengths of the two structures.

Hadji Yono-Cruz 2L
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Joined: Fri Sep 28, 2018 12:26 am

Re: Bond Lengths

Postby Hadji Yono-Cruz 2L » Sat Dec 01, 2018 6:15 pm

You can add the bond lengths together and divide by the total amount of resonance structures to find the average bond length.


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