# What is the empirical formula of P_4O_10?

${P}_{2} {O}_{5}$
By definition, $\text{the empirical formula}$ is the simplest whole number that defines constituent atoms in a species. The molecular formula is always a whole number multiple of the empirical formula. Of course, the multiple may be $1$.
Can you give me empirical formulae for $N {a}_{2} {O}_{2}$, ${C}_{4} {H}_{10}$, ${C}_{6} {H}_{6}$?