Why is uranium hexafluoride useful in gaseous diffusion?

Uranium hexafluoride (${\text{UF}}_6$) is utilized in the gaseous diffusion process because it is a volatile compound with an unusually high vapor pressure, allowing it to exist as a gas.12

This property is essential for isotope separation, a process required to enrich natural uranium in the fissionable isotope ${}^{235}\text{U}$. According to the kinetic theory of gases, at a given temperature, lighter molecules travel at a higher average velocity than heavier ones. Because ${}^{235}{\text{UF}}_6$ molecules are lighter than ${}^{238}{\text{UF}}_6$ molecules, they diffuse through a porous barrier more rapidly. By repeatedly diffusing the gas through these barriers, the concentration of ${}^{235}\text{U}$ can be increased to levels necessary for use in nuclear reactors and weapons.34