Radon is a noble gas but still radioactive. Why?

Radioactivity is a property of the nucleus of the atoms. However, radon is a noble gas because it cannot form chemical compounds. To do this, chemical reactions should be possible and this is connected with the atoms crust. So, due its electron configuration radon is chemically stable. read more

Radon is the noble gas which occurs naturally in radioactive form, being a decay product of U238. It is not really practical for industrial use because all its isotopes have very short half-lives, the longest being 3.8 days. read more

Radon is a chemical element with symbol Rn and atomic number 86. It is a radioactive, colorless, odorless, tasteless noble gas. It occurs naturally as an intermediate step in the normal radioactive decay chains through which thorium and uranium slowly decay into lead; radon, itself, is a decay product of radium. read more