Formal Charge & Stable lewis structures


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abbydouglas1K
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Formal Charge & Stable lewis structures

Postby abbydouglas1K » Thu Nov 08, 2018 10:41 am

When you calculate the formal charge I know that boy the end ll of the each individual changes must add up to the overall charge of molecule/ion. However if they add up does that means it is in its most stable or should you and try and make it so that you reduce the number of formal charges you have overall ?

Raymond Ko 1H
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Re: Formal Charge & Stable lewis structures

Postby Raymond Ko 1H » Thu Nov 08, 2018 10:59 am

The goal is to have the sum of all the formal charges of the atoms in the molecule add up to the actual charge of the molecule. When determining the formal charges for each individual atom, I think it is most ideal for each atom to have a minimum charge. For example, it would be a more stable Lewis structure for an oxygen atom to have a -1 formal charge rather than a -3 formal charge, even though it may add up to the actual charge of the molecule. It is more stable for several atoms to have a minimal formal charge in this case.

Andonios Karas 4H
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Re: Formal Charge & Stable lewis structures

Postby Andonios Karas 4H » Thu Nov 08, 2018 11:08 am

It is best to reduce the the formal charges overall because it lowers the difference in formal charge between two atoms in a molecule, which is more stable. For example, having one 2+ atom surrounded by two 1- atoms is typically less stable than all the atoms have a formal charge of zero.

Additionally, if you do end up with a Lewis structure that requires some atoms to have a formal charge other than 0, it is better to give - charges to the most electronegative atoms and + charges to the least electronegative atoms.

Kobe_Wright
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Re: Formal Charge & Stable lewis structures

Postby Kobe_Wright » Thu Nov 08, 2018 11:11 am

Just try to limit the amount of charges, and the quantity of that charge as much as possible as that shows the most stable structure but yes the charges should add up from each atom to the overall formal charge. Also make sure that if you have to make a decision about where to put - or + charges then be sure to put - on the most electronegative and + on the most electropositive.

shaunajava2e
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Re: Formal Charge & Stable lewis structures

Postby shaunajava2e » Thu Nov 08, 2018 11:18 am

the goal is to make the formal charge for each element 0 or as close to 0 as possible. if after calculating the formal charges of each element in the compound there are no elements with 0 formal charges, there is likely a better structure that can be shown.

Ariel Cheng 2I
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Re: Formal Charge & Stable lewis structures

Postby Ariel Cheng 2I » Thu Nov 08, 2018 1:01 pm

To add on to the previous posts, it is also most desirable to have the lowest possible charge on the central atom for stability though this is not always possible.

leediane0916
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Re: Formal Charge & Stable lewis structures

Postby leediane0916 » Thu Nov 08, 2018 5:12 pm

the formal charges need to add up to the charge of the entire molecule but the most stable structure is the one where the most atoms contain a FC =0


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