Ununtrium (IPA: /ˌjuːˈnʌntriəm/), or eka-thallium, is the temporary name of a synthetic element in the periodic table that has the temporary symbol Uut and has the atomic number 113. It comes from the alpha decay (release of a helium nucleus) of ununpentium. Following periodic trends it is expected to be a soft, silvery highly reactive metal, rather like sodium.