Octet vs Formal Charge

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Leah Savage 2F
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Octet vs Formal Charge

Postby Leah Savage 2F » Fri Dec 08, 2017 2:53 pm

Is it always better for all the atoms in a molecule to have an octet and possibly have formal charges than for them to have 0 formal charge but more than an octet? For example, in O3, or ozone, is the reason that there aren't 2 double bonds because the central O would have more than an octet? Because if there were double bonds all of the formal charges would be 0.

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Re: Octet vs Formal Charge

Postby SantanaRodriguezDis1G » Fri Dec 08, 2017 3:09 pm

some elements have to follow the octet rule, and you need to make sure that the formal charge adds up to the total charge

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Re: Octet vs Formal Charge

Postby Mirrat » Fri Dec 08, 2017 3:17 pm

Generally, a lower formal charge indicates a more stable molecule, so a structure which gives a lower formal charge would be preferred but if you have molecules with atoms from group 1 and 2, they cant have an expanded octet and need to obey the octet rule, so a formal charge that is not zero is okay. Ozone obeys the octet rule and in order for it to do this it needs to have at least one charged oxygen in the structure and hence there are not two double bonds in the structure (total number of electrons can only be 18) with the result that each oxygen in O3 ends up having a different formal charge (0, +1 and -1). Also, oxygen is pretty electronegative and we don't want it making 2 double bonds because that would give it a +2 FC.

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