formal charge

[Sophia Dinh 1D]

How can you determine the formal charge without the equation?

[Kallista McCarty 1C]

You count the number of bonds that the element has and compare it to the number of valence electrons that it should have!

[Ananta3G]

If you already have the Lewis Dot Drawing of the molecules correctly completed, you can just count the number of electrons around the atom by counting up each electron of the lone pair as one electron and each bonded pair as one electron as well ie 1 for a single bond, 2 for a double bond, etc. and compare that sum to the number of valence electrons you know the atom should have according to the periodic table to get the formal charge.

[MAC 4G]

Either way is fine if you get to the correct answer, but on an exam I think it's better to write out using the formula because in doing so, I believe it'll get you some partial credit if you were to make a mistake when drawing a Lewis structure or a resonance hybrid.

[kristi le 2F]

Also, with enough practice, you can remember how many lone pairs and bonding pairs like to have. For example, Oxygen likes to have 2 lone pairs and 2 bonding pairs because this gives it a formal charge of zero.

[505106414]

A very simplified/juvenile way to think of formal charge is FC = Valence E - (# sticks + # dots). Sticks being bonds and dots being single electrons in lone pairs.

[anjali41]

First you should look at the periodic table and determine how many valence electrons that the element should have. Next, count the total electrons present in the form of both lone pairs and bonds. Then compare this to the ideal number of valence electrons that the element should have. If there are more electrons, the formal charge will be negative. If there are fewer electrons present, then the formal charge will be positive.