A chemical element, symbol Sg, atomic number 106. Seaborgium has chemical properties similar to tungsten. It was synthesized and identified in 1974. This is the fourteenth of the synthetic transuranium elements, the laboratory-made elements heavier than uranium. Uranium is the heaviest commonly occurring element in nature (traces of plutonium, atomic number 94, have been detected in nature), having the atomic number 92. The lightest transuranium element, neptunium, with atomic number 93, was synthesized first in 1940, and the heaviest previous transuranium element, dubnium with atomic number 105, was synthesized in 1970.