## Best Formal Charge Equations

$FC=V-(L+\frac{S}{2})$

Jaclyn Schwartz 1I
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Joined: Wed Sep 30, 2020 9:45 pm

### Best Formal Charge Equations

What are some good formal charge equations? Or easier ways to remember them? Cuz I have seen multiple ways people find the formal charge and a tad confused.

Savana Maxfield 3F
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### Re: Best Formal Charge Equations

I calculate formal charge by: number of valence electrons - number of nonbonding electrons - (1/2) bonding electrons

Nathaly Cruz 2D
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Joined: Wed Sep 30, 2020 10:06 pm

### Re: Best Formal Charge Equations

Savana Maxfield 1G wrote:I calculate formal charge by: number of valence electrons - number of nonbonding electrons - (1/2) bonding electrons

I was struggling with formal charge and this equation really helped me understand it :)

Hayden Lee 1C
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Joined: Wed Sep 30, 2020 9:57 pm

### Re: Best Formal Charge Equations

The way that I calculate the formal charge is by using the following equation:

Formal Charge = (Valence e-) - (Nonbinding Valence e-) - (Bonding e-)*1/2

I suppose that one way to more easily memorize this equation is to memorize its abbreviated form (FC = V - NB - B/2). Hope this helps!

Jonathan Malau 1F
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Joined: Wed Sep 30, 2020 9:31 pm

### Re: Best Formal Charge Equations

For formal charge, I use: V - (s/2 + L). This is where v represents number of valence electrons, s signifies number of shared electrons, and L for number of lone pair electrons

Mackenzie Stockton 2H
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### Re: Best Formal Charge Equations

The best way to calculate formal charge is (number of valence electrons) - (dots) - (lines). Professor Lavelle covered another formula in class, but the formula I provided gives the same answer and is a lot faster.

Joshua Eidam 2A
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Joined: Wed Sep 30, 2020 9:58 pm

### Re: Best Formal Charge Equations

I agree with the previously mentioned equation using dots and lines. By counting each dot and line as 1, there is less confusion (at least for me) in terms of what value do I subtract from the valence electrons.

Kiyoka Kim 3C
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Joined: Wed Sep 30, 2020 9:59 pm

### Re: Best Formal Charge Equations

I usually calculate formal charge by FC = valence electrons - number of dots - number of bonds/lines.

Sejal Parsi 3K
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Joined: Wed Sep 30, 2020 10:03 pm

### Re: Best Formal Charge Equations

I agree with the dots and lines method as well. It seems easier to understand and do as well, counting each dot and line as 1.

Veeda Khan 2E
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### Re: Best Formal Charge Equations

I use VE= # of electrons - number of bonds.

Serena Song 1A
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### Re: Best Formal Charge Equations

I like using the FC = # of VE - # of dots - # of lines equation as well! I find it to the the fastest method once the lewis structure is drawn out.

Hannah Rim 2D
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### Re: Best Formal Charge Equations

Hey! I calculate formal charge by doing FC=valence electrons - (dots + lines/bonds). I like to count the dots individually and the lines (bonds) only count for when when doing formal charge.

Posts: 170
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### Re: Best Formal Charge Equations

For formal charge, if I am in a hurry, I just count the lone pair electrons and then one electron for each bond pair and if it gained an electron I know it is -1 and if it lost an electron I know it is +1. So for a single bonded oxygen I count the 6 lone pair electrons and the 1 electron from the bonding pair and I am able to tell that the fc is -1 without doing the formula.

Not sure if this makes sense but hope it helps.

Posts: 71
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### Re: Best Formal Charge Equations

The easiest way for me to find formal charge is to count! I start with the number of valence electrons the atom has, then I start in the middle at the atom and start counting down by one for each “thing” around the atom. For example, if nitrogen was surrounded by 3 bonds and 1 lone pair, you would start at the N and say 5, then count the bonds, 4, 3, 2, then count the lone pairs, 1, 0. So, Nitrogen would have a formal charge of 0 in this case! Hope this helps.

Will Skinner
Posts: 89
Joined: Wed Sep 30, 2020 9:28 pm

### Re: Best Formal Charge Equations

I don’t think finding the formal charge gets much simpler than the equation:
(#valence e-) - (#lone e-) - (1/2 #bonding e-)

For the last term in the equation (1/2 of bonding electrons), I find it easier to just count the number of lines connected to the atom in question on the Lewis structure.

Brianna Chen 3F
Posts: 103
Joined: Wed Sep 30, 2020 10:11 pm

### Re: Best Formal Charge Equations

The simplest way I have come up with calculating formal charge is with the following equation:
Formal charge = # of valence electrons - (# of "things" around the atom) These things correlate to lines/dots. Therefore, I simply count up how many lines and dots there are around the atom and subtract that from the number of valence electrons.

Eliana Carney 3E
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Joined: Wed Sep 30, 2020 9:31 pm

### Re: Best Formal Charge Equations

Hey Jaclyn!

The formula for formal charge that Dr. Lavelle gives in lectures is: formal charge = valence electrons - ((shared electrons/2) + lone pair electrons). While this formula works, it is a little hard to remember. Instead of this formula, I like to think of formal charge as: formal charge = valence electrons - "things". Here, "things" refers to everything that is attached to the atom in the Lewis structure. Essentially, each dot counts as one "thing" and each bond counts as one "thing" as well. You add up the number of dots and number of bonds to get the number of "things". Hope this helps!

(I also want to add that I didn't come up with this, I learned it in a UA session)

Hannah Chang 3K
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### Re: Best Formal Charge Equations

I use the equation the same way Dr. Lavelle uses during the lecture. FC=V-(shared/2+L)

305572629
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### Re: Best Formal Charge Equations

the equation that I use is "valence electrons on the periodic table - lines - dots"

Simi Kapila_3E
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### Re: Best Formal Charge Equations

I think the easiest way to calculate would just be the valence electrons -(number of bonds or lines) - (number of lone pair electrons or dots) to give you formal charge

Joshua Chung 2D
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### Re: Best Formal Charge Equations

Personally, I take the number of valence electrons (V) and subtract from it the number of bonds (s/2) combined with the number of non-bonding electrons (L).

Daniela Santana 2L
Posts: 96
Joined: Wed Sep 30, 2020 9:59 pm

### Re: Best Formal Charge Equations

I find the formal charge with this equation:

FC(of certain element in a structure): V(amount of valence electrons it has) - (Lone electrons it has + amount of bonds it shares with another element in the structure divided by 2)

I would recommend trying out different ways of calculating the formal charge with practice problems until you find the one that you like the best. Hope this helped :)

George Hernandez 3I
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### Re: Best Formal Charge Equations

A way to understand the concept of formal charge mentally is to comprehend whether an atom has gained or lost electrons. If you see an oxygen atom with 3 lone pairs and a single bond, for instance, you should be able to 'eyeball' that the atom has a formal charge of -1 because oxygen is supposed to have 6 valence electrons, however his situation shows it has one extra (6 valence and 1 covalent bond which means it originally had 7 electrons).

Jeremy Wei 2C
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### Re: Best Formal Charge Equations

Hi, for formal charge I also use the lines/dots way FC = valence electrons - # dots - # bonds/lines since it gives me more of a visual picture that helps me with picturing the charge.

Annette Fishman
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### Re: Best Formal Charge Equations

FC = valence electrons - number of dots - number of bonds/lines.