How many valence electrons does radon (Rn) have?
Radon is a noble gas with 8 valence electrons – an octet. An octet is the “ideal” number of valence electrons. This means that Radon doesn’t react* with other elements, because it doesn’t need to gain or lose electrons to reach the ideal number.
*Radon can be manipulated in a laboratory setting (forced) to react with other elements, this is very rare in nature.