London dispersion forces, also known as van der Waals forces, arise from temporary fluctuations in electron distribution within atoms or molecules. These forces are present in all substances, including noble gases like helium (He) and radon (Rn).
The strength of London dispersion forces depends on several factors, including the size of the atoms or molecules involved and the number of electrons they have. In general, larger atoms or molecules with more electrons tend to exhibit stronger London dispersion forces.
When comparing helium and radon, radon is significantly larger and heavier than helium. Radon has a larger atomic radius and a greater number of electrons compared to helium. The larger size and greater electron count of radon result in a higher polarizability, which refers to the ease with which the electron cloud of an atom or molecule can be distorted.
The increased polarizability of radon leads to stronger London dispersion forces compared to helium. The larger electron cloud of radon allows for greater temporary fluctuations in electron distribution, creating stronger instantaneous dipoles. These temporary dipoles induce corresponding dipoles in neighboring atoms or molecules, leading to attractive forces.
In summary, the larger size and greater number of electrons in radon contribute to its higher polarizability and, consequently, stronger London dispersion forces compared to helium.