Purpose of Formal Charge

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Ellis Song 4I
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Joined: Thu Jul 11, 2019 12:17 am

Purpose of Formal Charge

Postby Ellis Song 4I » Sun Nov 03, 2019 10:39 am

What is the purpose of formal charge? I know how to calculate it but what exactly is it for?

Posts: 51
Joined: Wed Sep 18, 2019 12:18 am

Re: Purpose of Formal Charge

Postby AprilPaz » Sun Nov 03, 2019 10:48 am

The purpose of calculating formal charge is to allow you to check if your lewis structure has the lowest energy possible. The least amount of formal charges you have the better.

Frederick Keith_4C
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Joined: Thu Sep 26, 2019 12:19 am

Re: Purpose of Formal Charge

Postby Frederick Keith_4C » Sun Nov 03, 2019 1:53 pm

A formal charge is the charge assigned to an atom in a molecule, assuming the electrons in a chemical bond are shared equally between the atoms. You know how to calculate it, but the purpose of it is to determine which of the Lewis structures it the most stable/correct. The lower the formal charge, the more stable the structure.

Janet Nguy 2C
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Joined: Sat Aug 24, 2019 12:17 am

Re: Purpose of Formal Charge

Postby Janet Nguy 2C » Sun Nov 03, 2019 2:08 pm

Assigning formal charge allows you to determine the most stable and accurate lewis structure for the compound. There can be multiple valid/correct ways to draw a Lewis structure for something, but the lowest energy model (which you use formal charges to find) will be a better representation of what the compound actually looks like.

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Joined: Thu Jul 25, 2019 12:16 am

Re: Purpose of Formal Charge

Postby zoedfinch1K » Sun Nov 03, 2019 2:43 pm

The purpose is to get the formal charge as closest to 0 as possible in order to find the most "correct" Lewis structure.

Bradley Whitworth 4B
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Re: Purpose of Formal Charge

Postby Bradley Whitworth 4B » Sun Nov 03, 2019 3:30 pm

The point of formal charge is to make sure you are drawing the most stable and hence most likely version of a molecule you would see in nature. For example, if you draw a molecule one way and the formal charges of two atoms are 2+ and 2- they cancel out. However, if you draw the molecule another way you find the formal charges of two atoms are 1+ and 1-. In both cases the formal charges cancel out but in the case where the charges are 1+ and 1- there is less overall formal charge within the molecule which means it is more stable.

Helen Struble 2F
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Joined: Sat Aug 24, 2019 12:17 am

Re: Purpose of Formal Charge

Postby Helen Struble 2F » Sun Nov 03, 2019 6:01 pm

Formal charge allows us to find the most likely molecular structure when there are multiple valid Lewis structures. Among the valid Lewis structure, the structure with FC closest to 0 is the most likely arrangement of atoms. It is super important to note that this is not the same as resonance or electron delocalization. The difference in FC actually corresponds to structural differences, in using FC to compare structure, we can determine the most likely molecular structure.

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