Oxygen was discovered by the Swedish chemist, Carl Wilhelm Scheele, in about 1772, although Joseph Priestly, who discovered the element independently in 1774, published his findings first. It is probable that several scientists had prepared the gas even earlier, without fully understanding what they had achieved. Leonardo da Vinci, in the fifteenth century, noted that air contained a gas that allowed combustion.
Sulphur, like other elements that are found free in nature, has been known since ancient times. It is mentioned several times in the Bible, and was first used in gunpowder in Europe in the thirteenth century. It was first described as an element by Antoine Laurent Lavoisier in 1777, although more than thirty years passed before this was confirmed.
Tellurium was discovered in 1782 by the Austrian mining inspector, Franz Joseph Muller von Reichenstein, and selenium was discovered by the Swedish chemist, J÷ns Jacob Berzelius, in 1818. The resemblances between the two elements are acknowledged in their names: tellurium derives its name from the Latin word, {Itellus}, meaning 'earth'; and selenium derives its name from the Greek word, {Iselene}, meaning 'the moon'.
Polonium was the first element to be discovered by means of its radioactivity. It was isolated from pitchblende in 1898 by the French scientists, Marie and Pierre Curie.
