Formal Charges

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aphung1G
Posts: 51
Joined: Sat Aug 24, 2019 12:15 am

Formal Charges

Postby aphung1G » Thu Nov 07, 2019 10:02 pm

Is it better for the central atom to have a +/- charge or have the other atoms take the +/- charge? And if so, why?

Abhi Vempati 4D
Posts: 51
Joined: Fri Aug 09, 2019 12:17 am

Re: Formal Charges

Postby Abhi Vempati 4D » Thu Nov 07, 2019 10:15 pm

The +/- charge doesn't really depend on the central atom. Instead, it depends on the electronegativity of the atoms. You want the most electronegative atom to have a - charge on in, so for something like PO43-, it wouldn't be the P that has a negative formal charge, but rather the oxygens around the P atom (3 oxygens out of the 4, to be specific) because they are more electronegative.

Lindsey Chheng 1H
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Joined: Fri Aug 30, 2019 12:16 am

Re: Formal Charges

Postby Lindsey Chheng 1H » Thu Nov 07, 2019 11:53 pm

aphung1G wrote:Is it better for the central atom to have a +/- charge or have the other atoms take the +/- charge? And if so, why?

Dr Lavelle said that typically, charges are held by the outer atoms in a Lewis structure.

andrewcj 4I
Posts: 51
Joined: Thu Jul 11, 2019 12:17 am

Re: Formal Charges

Postby andrewcj 4I » Fri Nov 08, 2019 2:18 am

Recall the rules for drawing Lewis structures. The central atom is the one that is the least electronegative, which means it has the least electron pulling power. Therefore, it would probably be best for it to not have a negative charge.

Manav Govil 4A
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Joined: Sat Sep 07, 2019 12:19 am

Re: Formal Charges

Postby Manav Govil 4A » Fri Nov 08, 2019 1:29 pm

It is best to have the negative charge on the most electronegative atom in the molecule, and the positive charge on the least electronegative atom in the molecule.

505106414
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Joined: Wed Sep 18, 2019 12:17 am

Re: Formal Charges

Postby 505106414 » Fri Nov 08, 2019 1:44 pm

Is it okay to break the octet rule in order to minimize formal charge?

Astrid Lunde 1G
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Joined: Sat Sep 07, 2019 12:16 am

Re: Formal Charges

Postby Astrid Lunde 1G » Fri Nov 08, 2019 2:55 pm

505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?


No unless the atom itself is able to break the octet rule.

Emma Popescu 3D
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Joined: Wed Sep 11, 2019 12:16 am

Re: Formal Charges

Postby Emma Popescu 3D » Fri Nov 08, 2019 7:04 pm

505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?


You can break the octet rule only if the element can hold more than 8 electrons (starting 3p)

Sally Qiu 4l
Posts: 46
Joined: Fri Aug 30, 2019 12:18 am

Re: Formal Charges

Postby Sally Qiu 4l » Fri Nov 08, 2019 7:22 pm

the charge isn't necessarily for the central atom. the most electronegative atom should have the negative charge

Alice Chang 4B
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Joined: Fri Aug 30, 2019 12:18 am

Re: Formal Charges

Postby Alice Chang 4B » Fri Nov 08, 2019 8:05 pm

505106414 wrote:Is it okay to break the octet rule in order to minimize formal charge?

only if the atom is able to take less or more than 8.
For example, Hydrogen only takes 2 electrons, while any element with a 3d-orbital or after can take extra electrons (more than 8).

MBouwman_4A
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Joined: Wed Sep 18, 2019 12:21 am

Re: Formal Charges

Postby MBouwman_4A » Sat Nov 09, 2019 5:25 pm

Since the central atom is usually the least electronegative, the surrounding atoms would have the charge.

Rebekah Alfred 1L
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Joined: Thu Jul 11, 2019 12:15 am

Re: Formal Charges

Postby Rebekah Alfred 1L » Sat Nov 09, 2019 5:33 pm

You generally want to avoid putting a negative formal charge on a central atom.

Amanda Ung 4D
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Joined: Thu Jul 25, 2019 12:17 am

Re: Formal Charges

Postby Amanda Ung 4D » Sun Nov 10, 2019 4:34 pm

Avoid putting the negative charge on the central atom but try to make most of the formal charges equal 0!

305376058
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Joined: Thu Jul 11, 2019 12:17 am

Re: Formal Charges

Postby 305376058 » Sun Nov 10, 2019 8:42 pm

Since the central atom is typically the least electronegative, it probably should not have a negative charge. I think that, in general, it is best for the central atom not to have a formal charge.

Caitlin Ciardelli 3E
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Joined: Wed Sep 18, 2019 12:19 am

Re: Formal Charges

Postby Caitlin Ciardelli 3E » Mon Nov 11, 2019 12:41 am

First, you want to avoid charges at all costs unless the molecule has a charge. If the molecule has a charge and you need to put charge somewhere, do not put it on the central atoms since this is the least electronegative. It also makes sense to have a charge on the outside atoms because these will be the electrons that interact with other charged molecules that come into contact with it.

Noah Canio 3C
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Joined: Wed Sep 18, 2019 12:20 am

Re: Formal Charges

Postby Noah Canio 3C » Mon Nov 11, 2019 12:47 am

In the case that it's impossible for the compound to not have nonzero values for its formal charges, then the negative charges must be delegated to the compound's most electronegative atoms while the least ones will typically have positive formal charges. For compounds with neutral charges, these formal charges should always add up to zero. For ions with charges, these formal charges should add up to the actual charge of the ion.


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