Formal Charge Practice Worksheet
A Grade 10 Science worksheet focusing on understanding and calculating formal charges in molecules and ions.
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Formal Charge Practice Worksheet
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Read each question carefully and follow the instructions to calculate formal charges and determine the most stable Lewis structures.
1. The formal charge of an atom in a molecule is the hypothetical charge it would have if all electrons in a bond were shared between the atoms.
2. To calculate formal charge, you subtract the number of non-bonding electrons and the number of bonding electrons from the number of valence electrons.
3. The sum of the formal charges in a neutral molecule must equal .
4. The sum of the formal charges in an ion must equal the of the ion.
5. Draw the Lewis structure for carbon dioxide (CO2). Calculate the formal charge on each atom in the molecule. Show your work.
6. Draw the Lewis structure for the cyanide ion (CN-). Calculate the formal charge on each atom in the ion. Show your work.
7. Which of the following is generally considered the most stable Lewis structure based on formal charges?
Structures with large formal charges
Structures where formal charges are minimized
Structures where all atoms have a positive formal charge
Structures with formal charges that sum to a negative value
8. For a molecule with multiple possible Lewis structures, how do formal charges help determine the most plausible structure?
The structure with the most positive formal charges is preferred.
The structure with formal charges closest to zero on all atoms is preferred.
The structure with negative formal charges on less electronegative atoms is preferred.
Formal charges are not useful for determining the most plausible structure.
9. A formal charge of zero on an atom indicates that the atom has the same number of electrons in the Lewis structure as it does in a neutral isolated atom.
True
False
10. In a Lewis structure, it is always best to place negative formal charges on the most electronegative atoms.
True
False
11. Draw all possible resonance structures for the thiocyanate ion (SCN-). Calculate the formal charge on each atom in each resonance structure. Identify the most stable resonance structure and explain why.