The number of bonds around carbon is 3.

The number of non-bonded electrons is two (it has a lone pair).

The number of valence electrons for carbon is 4.

LetвЂ™s apply it to :CH 3 (one to the right from BH 4) The formal charge of B in BH 4 is negative 1.

ДЄpplying this again to BH 4 (top left corner). So we can instead use this shortcut formula:ДЇormal Charge = вЂ“. Since a chemical bond has two electrons, the вЂњnumber of bonding electrons divided by 2вЂќ is by definition equal to the number of bonds surrounding the atom. There is a slightly easier way to do this, however. The total number of bonding electrons around boron is 8 (full octet).The number of non-bonded electrons is zero.

The number of valence electrons for boron is 3.This formula explicitly spells out the relationship between the number of bonding electrons and their relationship to how many are formally вЂњownedвЂќ by the atom.ДЇor example, applying this to BH 4 (top left corner in the image below) we get: Need to figure out if an atom is negative, positive, or neutral? HereвЂ™s the formula for figuring out the вЂњformal chargeвЂќ of an atom:ДЇormal charge = вЂ“ However, you might find my videos containing 10 solved examples of formal charge problems to be even more useful. In thisВ blog post I explainВ how to calculate formal charge for molecules. Hey! Welcome to Master Organic Chemistry, just in case youвЂ™re a first time visitor.

Formal charge formula