Five more elements that were first created artificially are strictly speaking not synthetic because they were later found in nature in trace quantities: 43 Tc, 61 Pm, 85 At, 93 Np, and 94 Pu, though are sometimes classified as synthetic alongside exclusively artificial elements. The first, technetium, was created in 1937. Plutonium (Pu, atomic number 94), first synthesized in 1940, is another such element. It is the element with the largest number of protons (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 mainly for its use in atomic bombs and nuclear reactors.