Formal Charge variables?

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Formal Charge variables?

Postby Saleha_Mian_3E » Wed Oct 31, 2018 3:04 pm

I know that the formal charge of an atom indicates a gain or loss of an electron while forming a covalent bond. And the equation is FC=V-(L+(S/2)) but what do the variables in the equation stand for? and could you provide an example.

JT Wechsler 2B
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Joined: Fri Sep 28, 2018 12:16 am

Re: Formal Charge variables?

Postby JT Wechsler 2B » Wed Oct 31, 2018 3:11 pm

V is the valence electrons that can be known by looking at the periodic table
L is the number of lone pair electrons
S is the number of electrons involved in bonding

For H2O, Oxygen is bonded to hydrogen with two single bonds.
Oxygen (from the periodic table) has 6 valence e-
It has 2 bonds (each with two electrons per bond) 4/2 = 2 e-
It has 4 lone pair electrons for a formal charge of 6-(4+(4/2)) = 0

Emmaraf 1K
Posts: 94
Joined: Sat Oct 20, 2018 12:16 am

Re: Formal Charge variables?

Postby Emmaraf 1K » Wed Oct 31, 2018 4:58 pm

Another easy way to calculate formal charge is to just do Valence electrons - # of bonds - number unpaired electrons = formal charge since then you don't have to divide by 2 when counting# bonded electrons. It speeds up the calculation and makes you less prone to making mistakes in my opinion.

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