Question

In naming a binary molecular compound, the number of atoms of each element present in the molecule is indicated by what?

Answer 1

You use prefixes (from Greek).

Explanation:

Examples:
`CO_2=` carbon di- oxide
`CO=` carbon mono- oxide
`N_2O=` di- nitrogen mono- oxide
`P_2O_5=` di- phosphor penta- oxide

The prefixes meaning:
mono=1, di=2, tri=3, tetra=4, penta=6, hexa=6, hepta=7.

Mono is often left out, unless there are similar compounds with di, tri, or otherwise. Also mono-oxide is often shortened to monoxide.

Water would be called di-hydrogen mono-oxide.