What indicates the actual number of constituent atoms in a molecule?

Options

A. Empirical formula
B. Molecular formula
C. Empirical mass
D. Molecular mass

Explanation

To answer the question "What indicates the actual number of constituent atoms in a molecule?", we can follow these steps:

### Step 1: Understand the Definitions
- **Molecular Formula**: This formula shows the actual number of each type of atom in a molecule. For example, in glucose (C6H12O6), the molecular formula indicates there are 6 carbon atoms, 12 hydrogen atoms, and 6 oxygen atoms.

### Step 2: Differentiate Between Molecular and Empirical Formulas
- **Empirical Formula**: This represents the simplest whole-number ratio of the atoms in a compound. For glucose, the empirical formula is CH2O, which reflects the ratio of 1 carbon atom, 2 hydrogen atoms, and 1 oxygen atom.

### Step 3: Clarify Molecular Mass
- **Molecular Mass**: This is the sum of the atomic masses of all the atoms in a molecule, but it does not indicate the number of atoms directly. For glucose, the molecular mass would be calculated based on the molecular formula, but it is not what indicates the number of constituent atoms.

### Conclusion
- The **molecular formula** is what indicates the actual number of constituent atoms in a molecule.

### Final Answer
The actual number of constituent atoms in a molecule is indicated by the **molecular formula**.

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