Question

How would you calculate the formal charge of NH3?

Answer 1

One Nitrogen atom = `1` x `-3` (nitrogen's charge) = `-3`

Three hydrogen atoms = `3` x `+1` (hydrogen's charge) = `3`

`-3 + 3 = 0` (net charge of `NH_3`)

Explanation:

If you refer to a periodic table you'll see columns. The elements in hydrogen's column have a `+1` charge. The elements in nitrogen's column have a `-3` charge.

You can determine the charge of the nitrogen column by starting with the noble gases(charge = `0`) and counting down by column. Similarly the hydrogen column starts with `+1` while the next column to the right is `+2`.

Transition metals are typically `+3`, although there are a few exceptions.