Final answer:
In molecular compound nomenclature, Greek numerical prefixes indicate the number of atoms, and the prefix for the first element is only used if there is more than one atom.
Step-by-step explanation:
When naming a molecular compound, the number of atoms of each element is indicated by a Greek numerical prefix. The first element in the name is numbered only when more than one atom of that element is present.
To clarify, prefixes like mono-, di-, tri- etc., are used to convey the count of atoms in the compound. For instance, carbon dioxide (CO₂) indicates that there are two atoms of oxygen for each atom of carbon, and the prefix 'mono-' is typically omitted for the first element if there's only one atom, as in carbon monoxide (CO).