rather than discovered in nature, was technetium in 1937. This discovery filled a gap in the periodic table, and the fact that technetium has no stable isotopes explains its natural absence on Earth (and the gap). With the longest-lived isotope of technetium, 97Tc, having a 4.21-million-year half-life, no technetium remains from the formation of the Earth. Only minute traces of technetium occur naturally in Earth's crust—as a product of spontaneous fission of 238U, or from neutron capture in molybdenum—but technetium is present naturally in red giant stars. Curium The first entirely synthetic element to be made was curium, synthesized in 1944 by Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso by bombarding plutonium with alpha particles. Eight others Synthesis of americium, berkelium, and californium followed soon. Einsteinium and fermium were discovered by a team of scientists led by Albert Ghiorso in 1952 while studying the composition of radioactive debris from the detonation of the first hydrogen bomb. The isotopes synthesized were einsteinium-253, with a half-life of 20.5 days, and fermium-255, with a half-life of about 20 hours. The creation of mendelevium, nobelium, and lawrencium followed. Rutherfordium and dubnium During the height of the Cold War, teams from the Soviet Union and the United States independently created rutherfordium and dubnium. The naming and credit for synthesis of these elements remained unresolved for many years, but eventually shared credit was recognized by IUPAC/IUPAP in 1992. In 1997, IUPAC decided to give dubnium its current name honoring the city of Dubna where the Russian team worked since American-chosen names had already been used for many existing synthetic elements, while the name rutherfordium (chosen by the American team) was accepted for element 104. The last thirteen Meanwhile, the American team had created seaborgium, and the next six elements had been created by a German team: bohrium, hassium, meitnerium, darmstadtium, roentgenium, and copernicium. Element 113, nihonium, was created by a Japanese team; the last five known elements, flerovium, moscovium, livermorium, tennessine, and oganesson, were created by Russian–American collaborations and complete the seventh row of the periodic table. List of synthetic elements The following elements do not occur naturally on Earth. All are transuranium elements and have atomic numbers of 95 and higher. Other elements usually produced through synthesis All elements with atomic numbers 1 through 94 occur naturally at least in trace quantities, but the following elements are often produced through synthesis. Technetium, promethium,