Octet vs formal charge

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Jasmin Argueta 1K
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Octet vs formal charge

Postby Jasmin Argueta 1K » Thu Nov 08, 2018 7:03 pm

What is more important, having your molecules have a formal charge of zero or a full octet?

Jeffrey Xiao 4A
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Re: Octet vs formal charge

Postby Jeffrey Xiao 4A » Thu Nov 08, 2018 7:08 pm

Formal charge of zero because there are octet exceptions such as PCl5 or BH3 which means they won't have a complete octet but their formal charge will be zero instead so formal charge closest to zero should be the most important factor as complete octets are not always necessary.

g orloff 1J
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Re: Octet vs formal charge

Postby g orloff 1J » Thu Nov 08, 2018 7:32 pm

there are some exceptions to the octet rule so always make sure formal charge is closest to zero.

Manya Bali 4E
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Re: Octet vs formal charge

Postby Manya Bali 4E » Thu Nov 08, 2018 8:12 pm

What's already been mentioned is true, but you shouldn't get so caught up with making the formal charge 0 that you forget about the octet rule and its exceptions. For example, carbon would never have more than an octet. In that cases, it would be better to have some formal charge that is not 0 (but hopefully close to it!!) instead of giving carbon more than an octet since that wouldn't occur in real life (carbon only has s and p orbitals for electrons to go in which has a maximum of 8 electron slots.)

Vicky Lu 1L
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Re: Octet vs formal charge

Postby Vicky Lu 1L » Thu Nov 08, 2018 8:58 pm

I believe having the correct formal charge is more important than having a full octet. As seen in some examples with radicals and expanded octets, it is alright if the atom does not have an entire octet, however, your formal charges between the atoms should be equal to the formal charge of the molecule. The rule to the formal charge is more guaranteed in writing a Lewis structure since there are always exceptions to the octet rule.

Celine Hoh 2L
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Re: Octet vs formal charge

Postby Celine Hoh 2L » Thu Nov 08, 2018 9:16 pm

Also make sure that for elements that do not have expanded d orbitals (Period 2 and above) do not exceed their octet shell.

sarahartzell1k
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Re: Octet vs formal charge

Postby sarahartzell1k » Thu Nov 08, 2018 10:06 pm

It is important to make sure the formal charge is as accurate as possible but always be aware of the octet rule and its exceptions

Katie Sy 1L
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Re: Octet vs formal charge

Postby Katie Sy 1L » Thu Nov 08, 2018 10:50 pm

formal charge being 0 is more important because don't forget about elements that have octet exceptions

Jovian Cheung 1K
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Re: Octet vs formal charge

Postby Jovian Cheung 1K » Fri Nov 09, 2018 12:52 pm

It's actually hard to say which is more important.
Just reduce the formal charges to as close to zero as you can WHILE still abiding restrictions related to the octet rule. If the atoms can be an exception to the octet rule (like phosphorus which can expand its octet), then prioritise formal charges. If the atoms can't be an exception to the octet rule (e.g. the central atom can't expand its octet / not a radical / etc, etc), then you still have to abide to the octet rule.

For example, for NO3-, the formal charges would have been even closer to zero if there were two double bonds! But since nitrogen can't expand its octet, we can't do that.

Elena Saab 4A
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Re: Octet vs formal charge

Postby Elena Saab 4A » Fri Nov 09, 2018 1:01 pm

Is formal charge also more important than having resonance structure? How much does resonance affect stability?

Lucy Agnew 3E
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Re: Octet vs formal charge

Postby Lucy Agnew 3E » Fri Nov 09, 2018 1:13 pm

All these answers were really helpful thank you!!

105002507
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Joined: Fri Sep 28, 2018 12:15 am

Re: Octet vs formal charge

Postby 105002507 » Sun Nov 11, 2018 3:00 pm

I think formal charge is more important (with 0 being the most stable) because there are expections for certain elements regarding the octet rule

705022748
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Re: Octet vs formal charge

Postby 705022748 » Fri Nov 16, 2018 1:26 am

The accuracy of formal charge should be prioritized over having a full octet, because formal charge is usually more guaranteed while octet rule comes with exceptions.

Rylee Nelsen 3A
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Re: Octet vs formal charge

Postby Rylee Nelsen 3A » Fri Nov 16, 2018 9:28 am

I would say that finding the lowest possible formal charge to create the most stable Lewis structure is more important because there are various exceptions to the octet rule so you cannot always base where a structure is correct if each atom has a full octet.

MichelleTran 1I
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Re: Octet vs formal charge

Postby MichelleTran 1I » Sun Nov 25, 2018 1:10 pm

Having the lowest formal charge is more important because the molecule will be more stable overall. There are some exceptions to the octet rule as well, so generally, following the rule of lowest formal charge would be the better bet.

Tony Chung 2I
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Re: Octet vs formal charge

Postby Tony Chung 2I » Sun Dec 02, 2018 7:59 pm

having a formal charge of 0

205458163
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Joined: Wed Jun 26, 2019 12:15 am

Re: Octet vs formal charge

Postby 205458163 » Fri Jul 12, 2019 8:20 pm

Most of the time, these two conditions will exist together, but if under some special condition, formal charge is more important.


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