Formal Charge Practice Worksheet
A Grade 12 Chemistry worksheet focusing on calculating formal charges and predicting the most stable Lewis structures.
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Formal Charge Practice Worksheet
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Carefully read each question and follow the instructions. Show all your calculations for formal charge.
1. Formal charge is a hypothetical charge assigned to an atom in a molecule or polyatomic ion, assuming that electrons in all chemical bonds are shared between atoms.
2. The formula for formal charge is: Formal Charge = (Valence Electrons) - (Non-bonding Electrons) - (1/2 * Electrons).
3. The sum of the formal charges in a neutral molecule should always be .
4. The sum of the formal charges in a polyatomic ion should equal the of the ion.
5. Calculate the formal charge for each atom in the carbon dioxide (CO2) molecule. Draw the Lewis structure first.
6. For the cyanide ion (CN-), draw the most plausible Lewis structure and determine the formal charge on both the carbon and nitrogen atoms.
7. Which of the following statements is TRUE regarding the prediction of the most stable Lewis structure using formal charges?
The most stable structure has the largest number of atoms with non-zero formal charges.
The most stable structure places negative formal charges on the less electronegative atoms.
The most stable structure minimizes the number of atoms with non-zero formal charges.
Formal charges are not useful in predicting the stability of Lewis structures.
8. Formal charge is the actual charge of an atom in a molecule.
True
False
9. Consider the thiocyanate ion (SCN⁻). Draw three possible Lewis structures and assign formal charges to each atom in all three structures. Based on formal charges, identify the most stable Lewis structure.