Livermorium (Lv) is an artificial element, and thus a standard atomic mass cannot be given. Like all artificial elements, it has no stable isotopes. The first isotope to be synthesized was ²⁹³Lv in 2000. There are four known radioisotopes from ²⁹⁰Lv to ²⁹³Lv. The longest-lived isotope is ²⁹³Lv with a half-life of 53 ms.