## Bond Strength In Same Group

Chris Gris 3I
Posts: 21
Joined: Fri Sep 25, 2015 3:00 am

### Bond Strength In Same Group

I understand that bond strength is determined by bond length, and that triple bonds are stronger than double bonds, and double bonds stronger than single; however, I don't understand how you can determine which bond is stronger between two compounds with nearly identical Lewis structures but with different bonding elements from the same group. For example, how do you know whether the CCl4 or CBr4 bonds are stronger?

Annie Qing 2F
Posts: 28
Joined: Fri Sep 25, 2015 3:00 am

### Re: Bond Strength In Same Group

I might be wrong but I think to answer your question, the stronger bond is the one with the more electronegative atom involved. For instance, the $CCl_{4}$ bonds are stronger than those of the $CBr_{4}$ molecule because Cl is a more electronegative atom. Electronegative atoms hold electrons more tightly and therefore increase the strength of the bond, just like ionic bonds are stronger than covalent because one of the atoms in an ionic bond is usually very electronegative.

Posts: 25
Joined: Sat Jul 22, 2017 3:00 am

### Re: Bond Strength In Same Group

The solutions manual says that electronegativity and polarity arguments would predict the C-F bond to be weaker than the C-Br or C-Cl bond so I think there is another explanation. Does anyone know why?

Mariane Sanchez 1E
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Joined: Fri Sep 29, 2017 7:07 am

### Re: Bond Strength In Same Group

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### Re: Bond Strength In Same Group

Bond strength is also directly related to atom size. Larger atoms have a larger distance so a longer bond length, and because longer bonds are are weaker, large atoms form weaker bonds. So you can compare bond strength in a group because as you go down a group atom size increases. Therefore CCl4 would have stronger than CBr4.

Steven Luong 1E
Posts: 33
Joined: Fri Apr 06, 2018 11:03 am

### Re: Bond Strength In Same Group

The stronger bond is in the molecule with the more electronegative atom involved. For instance, the bonds in CCl4 are stronger than those of the CBr4 because Cl has a higher electronegativity than Br due to Cl's smaller size. Electronegative atoms hold electrons more tightly, thus increasing the strength of the bond.

Chris Qiu 1H
Posts: 31
Joined: Fri Apr 06, 2018 11:04 am

### Re: Bond Strength In Same Group

You go off of polarzability, if the elements that are bound in one instance have higher polarizability then they will create a stronger bond.

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