# Is H2O an empirical formula?

The empirical formula is the simplest whole number ratio that defines constituent atoms in a species (that was glib, I learned this definition as a youth!). Since $O {H}_{2}$ is the simplest whole number ratio it is indeed the empirical formula.
To expand, the molecular formula is always a multiple of the empirical formula: i.e $M . F . = n \left(E . F .\right)$, where $n$ is an integer. Here the multiple is $1$, because clearly the molecular formula of water is ${H}_{2} O$.
Can you tell me the empirical formulae of hydrogen peroxide, ${H}_{2} {O}_{2}$, $N O$, ${N}_{2} {O}_{4}$, and ${H}_{2} C = C {H}_{2}$?