1. A nitrogenous base: This is a molecule with a nitrogen-containing ring structure. There are five main types of nitrogenous bases found in nucleotides: adenine (A), guanine (G), cytosine (C), thymine (T), and uracil (U).

2. A five-carbon sugar: This is a sugar molecule with five carbon atoms. The most common sugar found in nucleotides is ribose, which is present in RNA. Deoxyribose, which is missing an oxygen atom compared to ribose, is present in DNA.

3. A phosphate group: This is a group of atoms consisting of one phosphorus atom and four oxygen atoms.

These three molecules are linked together in a specific order: the phosphate group is attached to the sugar molecule, and the nitrogenous base is attached to the sugar molecule.