We’re being asked to determine the **formal charge of ALL ELEMENTS **in **H _{3}O^{+}, SO_{4}^{2-} and NH_{3}.**

**To do so, we need to do the following steps:**

*Step 1:* Determine the central atom in the molecule.

*Step 2:* Calculate the total number of valence electrons present.

*Step 3:* Draw the Lewis structure for the molecule.

*Step 4:* Calculate the formal charge for the indicated atom.

Recall that the formula for the ** formal charge** is:

$\overline{){\mathbf{F}}{\mathbf{.}}{\mathbf{C}}{\mathbf{.}}{\mathbf{=}}{\mathbf{Group}}{\mathbf{}}{\mathbf{No}}{\mathbf{.}}{\mathbf{}}{\mathbf{-}}\left(\mathbf{Bonds}\mathbf{+}\mathbf{Nonbonding}\mathbf{}\mathbf{electrons}\right)}$

Determine the formal charge of each element in the following:

(a) H_{3}O^{+}

(b) SO_{4}^{2−}

(c) NH_{3}