Answer by
instantempo (6)
222Rn (Radon 222) is a stable Radon isotope. Discovered by Marie Curie, Radon222 is a radioactive gas with an half-life of 4 days. Although used in radioterapy, it is toxic. Small amounts naturally occur in nature: in fact Radon can accumulate in some buildings. Being a gas, the best way to keep it out is to change frequently the air.