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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.
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.
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.
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).
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.
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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