We are asked to** ****draw a Lewis structure that makes the formal charge on the central atom equal to zero**.

We are given that X is an element from the third period (Na-Ar). By changing the overall charge, n, from 1- to 2- to 3- we get three different polyatomic ions

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

*Step 1:* Determine the number of valence electrons and the identity of X.

*Step 2:* Determine the formal charge of X.

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

*Step 4:* Draw the Lewis structure that makes the formal charge on the central atom equal to zero.

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

$\overline{){\mathbf{F}}{\mathbf{.}}{\mathbf{C}}{\mathbf{.}}{\mathbf{=}}{\mathbf{Group}}{\mathbf{}}{\mathbf{Number}}{\mathbf{-}}\mathbf{(}\mathbf{Bonds}\mathbf{+}\mathbf{Nonbonding}\mathbf{}\mathbf{Electrons}\mathbf{)}}$

Consider the Lewis structure for the polyatomic oxyanion shown here, where X is an element from the third period (Na-Ar). By changing the overall charge, n, from 1- to 2- to 3- we get three different polyatomic ions.

For each of these ions draw a Lewis structure that makes the formal charge on the central atom equal to zero.

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