Which of the following best describes a formula unit in chemistry?

• A. The total number of atoms in a molecule.
• B. The empirical formula of any covalent compound.
• C. The smallest repeating unit in a molecular compound.
• D. The simplest whole-number ratio of ions represented in an ionic compound.

Answer: (D)

Verified step by step guidance

1. Understand that a formula unit refers specifically to ionic compounds, which are composed of ions rather than molecules.
2. Recall that ionic compounds do not exist as discrete molecules but as a repeating lattice of ions arranged in a pattern.
3. Recognize that the formula unit represents the simplest whole-number ratio of the ions in the ionic compound, not the total number of atoms or a molecular formula.
4. Differentiate between molecular compounds (which have molecules and molecular formulas) and ionic compounds (which have formula units and empirical formulas).
5. Conclude that the formula unit is best described as the simplest whole-number ratio of ions represented in an ionic compound.