Technetium The first element to be synthesized, 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==