Final answer:
Option D, CO2, is the molecular formula among the options, representing a compound with a specific number of atoms of each element in a single molecule.
Step-by-step explanation:
You asked which of the following options is a molecular formula: A.) Ca(OH)2 B.) AlCl3 C.) Na2CO3 D.) CO2. A molecular formula shows the exact number of atoms of each element in a single molecule of a compound. Option D, CO2, is a molecular formula and it represents one molecule of carbon dioxide, highlighting a 1:2 ratio of carbon to oxygen atoms.
Answers A, B, and C are not molecular formulas; they are ionic formulas because they represent ionic compounds. For instance, Ca(OH)2 is calcium hydroxide and is made up of one calcium atom, two oxygen atoms, and two hydrogen atoms, but since it's an ionic compound comprising calcium cations and hydroxide anions, its representation doesn't conform to the definition of a molecular formula.