A synthetic element is one of 24 known chemical elements that do not occur naturally on Earth: they have been created by human manipulation of fundamental particles in a nuclear reactor, a particle accelerator, or the explosion of an atomic bomb; thus, they are called "synthetic", "artificial", or "man-made". The synthetic elements are those with atomic numbers 95–118, as shown in purple on the accompanying periodic table: these 24 elements were first created between 1944 and 2010. The mechanism for the creation of a synthetic element is to force additional protons onto the nucleus of an element with an atomic number lower than 95. All synthetic elements are unstable, but they decay at widely varying rates: their half-lives range from a few hundred microseconds to millions of years. Five more elements that were created artificially are strictly speaking not synthetic because they were later discovered to exist in nature in trace quantities: 43Tc, 61Pm, 85At, 93Np, and 94Pu. However, they are sometimes labelled as synthetic anyway. The first, technetium (symbol Tc), was created in 1937. Plutonium (symbol Pu, atomic number 94), first synthesized in 1940, is another such element. It is the element with the largest number of protons (and equivalent atomic number) to occur in nature, but it does so in such tiny quantities that it is far more practical to synthesize it. Plutonium is known primarily for its use in atomic bombs and nuclear reactors. No elements with atomic numbers greater than 99 have any uses outside of scientific research, since they have extremely short half-lives, and thus have never been produced in large quantities.
