Dioxygen (normal oxygen,  $O_2$) and trioxygen (ozone, $O_3$ ) are allotropic forms.  Consider equal masses of  $O_2$ and $O_3$ .  The correct statements are: 

For equal masses, ratio of moles of  $O_2$  and  $O_3=\frac{1}{32}:\frac{1}{48}=3:2$ .
They contain different number of molecules.
At same temperature, and at same pressure, their volume ratio is  $3:2$
Ratio of number of atoms  $=(3\times 2):(2\times 3)=1:1$
Density, which is mass/volume, is different.