How can I calculate formal charge?

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How can I calculate formal charge?

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Answer 1 · 2014-10-28T20:04:09

The formula for calculating the formal charge on an atom is simple.

Formal charge = [# of valence electrons] – [electrons in lone pairs + 1/2 the number of bonding electrons]

Since the number of bonding electrons divided by 2 is equal to the number of bonds surrounding the atom, this formula can be shortened to:
Formal Charge = [# of valence electrons on atom] – [non-bonded electrons + number of bonds].

Let's look at an example. Take the compound $B H^{4}$ $BH^4$ , or tetrahydrdoborate. Boron, $(B)$ $(B)$ has 3 valence electrons, zero non-bonded electrons, and 4 bonds around it. This means that the formula becomes $3 - (0 + 4)$ $3-(0+4)$ , giving an answer of $- 1$ $-1$ .

Next, let's look at the hydrogen atoms in $B H^{4}$ $BH^4$ . Hydrogen has one valence electron, zero non bonded electrons, and one bond. So the formal charge of hydrogen in $B H^{4}$ $BH^4$ is $1 - (0 + 1)$ $1-(0+1)$ , which gives a formal charge of 0.

Sources: http://www.masterorganicchemistry.com/2010/09/24/how-to-calculate-formal-charge/

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How can I calculate formal charge?

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