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Formal Charges

Posted: Thu Nov 07, 2019 10:02 pm
by aphung1E
Is it better for the central atom to have a +/- charge or have the other atoms take the +/- charge? And if so, why?

Re: Formal Charges

Posted: Thu Nov 07, 2019 10:15 pm
by Abhi Vempati 2H
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.

Re: Formal Charges

Posted: Thu Nov 07, 2019 11:53 pm
by Lindsey Chheng 1E
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.

Re: Formal Charges

Posted: Fri Nov 08, 2019 2:18 am
by andrewcj 2C
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.

Re: Formal Charges

Posted: Fri Nov 08, 2019 1:29 pm
by Manav Govil 1B
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.

Re: Formal Charges

Posted: Fri Nov 08, 2019 1:44 pm
by 505106414
Is it okay to break the octet rule in order to minimize formal charge?

Re: Formal Charges

Posted: Fri Nov 08, 2019 2:55 pm
by Astrid Lunde 1I
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.

Re: Formal Charges

Posted: Fri Nov 08, 2019 7:04 pm
by Emma Popescu 1L
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)

Re: Formal Charges

Posted: Fri Nov 08, 2019 7:22 pm
by Sally Qiu 2E
the charge isn't necessarily for the central atom. the most electronegative atom should have the negative charge

Re: Formal Charges

Posted: Fri Nov 08, 2019 8:05 pm
by Alice Chang 2H
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).

Re: Formal Charges

Posted: Sat Nov 09, 2019 5:25 pm
by MBouwman_4A
Since the central atom is usually the least electronegative, the surrounding atoms would have the charge.

Re: Formal Charges

Posted: Sat Nov 09, 2019 5:33 pm
by Rebekah Alfred 1J
You generally want to avoid putting a negative formal charge on a central atom.

Re: Formal Charges

Posted: Sun Nov 10, 2019 4:34 pm
by Amanda Ung 4D
Avoid putting the negative charge on the central atom but try to make most of the formal charges equal 0!

Re: Formal Charges

Posted: Sun Nov 10, 2019 8:42 pm
by 305376058
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.

Re: Formal Charges

Posted: Mon Nov 11, 2019 12:41 am
by Caitlin Ciardelli 3E
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.

Re: Formal Charges

Posted: Mon Nov 11, 2019 12:47 am
by Noah Canio 3C
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.