Which one of the following statements about formal charge is true?

• A. Formal charge always indicates the actual charge on an atom in a molecule.
• B. Formal charge is determined solely by the electronegativity of the atom.
• C. Atoms in a molecule always have a formal charge of zero.
• D. Formal charge is calculated by subtracting the number of nonbonding electrons and half the number of bonding electrons from the number of valence electrons in the free atom.

Answer: (D)

Verified step by step guidance

1. Understand that formal charge is a bookkeeping tool used to estimate the charge distribution within a molecule, not necessarily the actual charge on an atom.
2. Recall the formula for calculating formal charge: \(\text{Formal Charge} = \text{Valence Electrons} - \text{Nonbonding Electrons} - \frac{1}{2} \times \text{Bonding Electrons}\).
3. Recognize that formal charge depends on the electron count around an atom compared to its valence electrons in the free (unbonded) state, and it does not depend solely on electronegativity.
4. Note that atoms in molecules can have formal charges other than zero; having a formal charge of zero is common but not mandatory.
5. Conclude that the true statement is the one describing the calculation method of formal charge using valence electrons, nonbonding electrons, and bonding electrons.