Oxygen (O), nonmetallic chemical element of Group 16 (VIa, or the oxygen group) of the periodic table. Oxygen is a colourless, odourless, tasteless gas essential to living organisms, being taken up by animals, which convert it to carbon dioxide; plants, in turn, utilize carbon dioxide as a source of carbon and return the oxygen to the atmosphere. Oxygen forms compounds by reaction with practically any other element, as well as by reactions that displace elements from their combinations with each other; in many cases, these processes are accompanied by the evolution of heat and light and in such cases are called combustions. Continue reading from Encyclopedia Britannica
In 1608, Cornelius Drebbel had shown that heating saltpetre (potassium nitrate, KNO3) released a gas. This was oxygen although it was not identified as such. The credit for discovering oxygen is now shared by three chemists: an Englishman, a Swede, and a Frenchman. Joseph Priestley was the first to publish an account of oxygen, having made it in 1774 by focussing sunlight on to mercuric oxide (HgO), and collecting the gas which came off. He noted that a candle burned more brightly in it and that it made breathing easier. Unknown to Priestly, Carl Wilhelm Scheele had produced oxygen in June 1771. He had written an account of his discovery but it was not published until 1777. Antoine Lavoisier also claimed to have discovered oxygen, and he proposed that the new gas be called oxy-gène, meaning acid-forming, because he thought it was the basis of all acids. Continue reading from Royal Society of Chemistry
Earth has been oxygenated for about 2.3 billion to 2.4 billion years, and levels began to creep up at least 2.5 billion years ago. As a gas, oxygen is clear. But as a liquid, it's pale blue. Oxygen forms in the hearts of stars, with the fusion of a carbon-12 nucleus and a helium-4 nucleus (also known as an alpha particle). It's only recently, however, that scientists have been able to peer into the nucleus of oxygen and unravel its structure. Continue reading from LiveScience
