Natural rubidium is similarly slightly radioactive, with 27.83% being the long-lived radioisotope rubidium-87.
nˈætʃɚɹəl ɹuːbˈɪdiəm ɪz sˈɪmɪlɚli slˈaɪtli ɹˌeɪdɪoʊˈæktɪv, wɪð twˈɛnti sˈɛvən.ˈeɪɾi θɹˈiː pɚsˈɛnt bˌiːɪŋ ðə lˈɔŋlˈɪvd ɹˌeɪdɪoʊˈaɪsətˌoʊp ɹuːbˈɪdiəm ˈeɪɾi sˈɛvən.