observation that there are no known half-lives suitable half-life unstable isotope rather short shelf life of six months this list rather short shelf life of six months rather short shelf life of six months Depending on which element you choose Depending on which element you choose rather short shelf life of six months deze lijst van vervaltijden op Wikipedia rather short shelf life of six months half-life of radioactive materials rather short shelf life of six months rather short shelf life of six months Depending on which element you choose halftime half life Depending on which element you choose unstable isotope