Which statement about isotopes is correct?

3.1.1. State the formulae of the elements and compounds named in the subject content

3.1.2. Define the molecular formula of a compound as the number and type of different atoms in one molecule

3.1.3. Deduce the formula of a simple compound from the relative numbers of atoms present in a model or a diagrammatic representation

3.1.4. Construct word equations and symbol equations to show how reactants form products, including state symbols

3.1.5. Define the empirical formula of a compound as the simplest whole number ratio of the different atoms or ions in a compound

3.1.6. Deduce the formula of an ionic compound from the relative numbers of the ions present in a model or a diagrammatic representation or from the charges on the ions

3.1.7. Construct symbol equations with state symbols, including ionic equations

3.1.8. Deduce the symbol equation with state symbols for a chemical reaction, given relevant information