## formal charge

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

nikitasridhar_1b
Posts: 42
Joined: Fri Apr 06, 2018 11:05 am

### formal charge

I wasn't able to attend lecture last class and am unsure about how to calculate formal charge. Is it just the number of electrons to add (resulting in a negative charge) or number of electrons to remove (resulting in a positive charge)

Betty Wolkeba section 1L
Posts: 32
Joined: Fri Apr 06, 2018 11:05 am

### Re: formal charge

I like to think of it as the number of valence electrons minus the sum of how many electrons there are around it on the lewis sturcture (a bond=1 electron, a lone pair of electrons =2). The charge would be more negative if there are more electrons required to fill the octet than the number of valence electrons the element has. Hope that helps a bit!

Emma Leshan 1B
Posts: 30
Joined: Fri Apr 06, 2018 11:03 am

### Re: formal charge

Formal charge = number of lone pair electrons - 1/2 * number of bonding electrons

Neha Divi 1K
Posts: 31
Joined: Fri Apr 06, 2018 11:02 am

### Re: formal charge

Formal charge can be calculated by looking at the number of electrons an atom wants and then subtracting each electron in lone pairs surrounding the atom and any electrons bonded (1 for each line in the lewis structure). In addition, the formula Dr. Lavelle stated in class was FC=V-(L+(S/2)).

804991762_4A
Posts: 47
Joined: Fri Apr 06, 2018 11:04 am

### Re: formal charge

When trying to minimize the formal charge, how do you know which element you should minimize first?

Hope_Pham_1G
Posts: 29
Joined: Fri Apr 06, 2018 11:04 am

### Re: formal charge

"When trying to minimize the formal charge, how do you know which element you should minimize first?"

According to my observation, it seems as if altering the bond arrangements affects the formal charge of multiple elements simultaneously. I don't think there is a specific order.

Jennifer Tuell 1B
Posts: 34
Joined: Fri Apr 06, 2018 11:05 am

### Re: formal charge

I know you can just count the bonds for the bonding electrons but I find it helpful to do the 1/2 times the bonding electrons just to make sure.

Maria Zamarripa 1L
Posts: 30
Joined: Fri Apr 06, 2018 11:05 am
Been upvoted: 1 time

### Re: formal charge

so the equation for formal charge is
formal charge= v-(L+(1/2(B))
v= # of valence electrons
L= # of Lone pairs
B= # of Bonded pairs

AlyssaRivera
Posts: 29
Joined: Fri Apr 06, 2018 11:04 am

### Re: formal charge

Finding the formal charge is super simple, even though the formula may look complicated. The formula is FC=V-(L+B/2) You take the lewis structure for the problem you are doing and look at the specific element that you're solving for, plug in the number of valence electrons that it should have based on the periodic table (V), the amount of lone pairs around that specific element based on the lewis structure(L), and the amount of electron pairs that are bonded in the lewis structure(B). Then solve and you're done, you shouldn't even need a calculator.

juliaschreib1A
Posts: 29
Joined: Fri Sep 29, 2017 7:06 am

### Re: formal charge

It is a lot easier to calculate formal charge as
FC= (The # of valence electrons the element comes with) - (The number of bonds/dots the electron has now)

Alicia Beebe
Posts: 37
Joined: Fri Apr 06, 2018 11:01 am

### Re: formal charge

I don't use the equation given at all. My way may make no sense to you, but heres a try. When looking at a lewis structure i determine formal charge by looking at two things. 1. I see how many times a line or dot is "touching the atom" in the Lewis structure, so a lone pair of 2 electrons would be 2, a single bond would be 1, and a double bond would be 2, and so on. 2. I then compare this number with the amount of valence electrons as expressed on the periodic table. For example, if I was looking at a lewis structure with N as the central atom, connected by two double bonds, that would mean there were four. I can compare this to on the periodic table that the N wants five, so the N has a charge of +1. I know this is a very roundabout way, but I thought it may work for someone!

Surya Palavali 1D
Posts: 24
Joined: Fri Apr 06, 2018 11:04 am

### Re: formal charge

Formal Charge = (Valence Electrons) - (Lone Pair Electrons) - (0.5 x Bonded Electrons)