## Octet vs formal charge

Jasmin Argueta 1K
Posts: 69
Joined: Fri Sep 28, 2018 12:16 am

### Octet vs formal charge

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

Jeffrey Xiao 4A
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Joined: Fri Sep 28, 2018 12:28 am
Been upvoted: 1 time

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:16 am

### Re: Octet vs formal charge

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

Manya Bali 4E
Posts: 66
Joined: Fri Sep 28, 2018 12:23 am

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:18 am

### Re: Octet vs formal charge

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
Posts: 66
Joined: Fri Sep 28, 2018 12:28 am

### Re: Octet vs formal charge

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

sarahartzell1A
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Joined: Fri Sep 28, 2018 12:17 am

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:18 am

### Re: Octet vs formal charge

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

Jovian Cheung 1K
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Joined: Fri Sep 28, 2018 12:16 am

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:27 am

### Re: Octet vs formal charge

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

Lucy Agnew 3E
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Joined: Fri Sep 28, 2018 12:26 am

### Re: Octet vs formal charge

105002507
Posts: 30
Joined: Fri Sep 28, 2018 12:15 am

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:25 am

### Re: Octet vs formal charge

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
Posts: 37
Joined: Fri Sep 28, 2018 12:22 am

### Re: Octet vs formal charge

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
Posts: 40
Joined: Fri Sep 28, 2018 12:23 am

### Re: Octet vs formal charge

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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Joined: Fri Sep 28, 2018 12:19 am

### Re: Octet vs formal charge

having a formal charge of 0

205458163
Posts: 33
Joined: Wed Jun 26, 2019 12:15 am

### Re: Octet vs formal charge

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