#OXYGEN ATOM FREE#

About 300 million years ago, when oxygen levels reached 35 percent, insects were able to grow super-large: Think dragonflies with the wingspans of hawks. Thank goodness for an atmosphere of 21 percent oxygen.The findings were published in the New England Journal of Medicine. Compare that to the normal value of 12 to 14 kilopascals, and the mountaineering term 'death zone' makes plenty of sense. Climbers had arterial oxygen levels of 3.28 kilopascals on average. The lowest levels of oxygen ever recorded in human blood were measured near the summit of Mount Everest in 2009.Oxygen is one tough cookie: A 2012 study published in the journal Physical Review Letters found than an oxygen molecule (O2) can survive pressures 19 million times higher than atmospheric pressure.Breathing 80 percent oxygen for more than 12 hours irritates the respiratory tract and can eventually cause deadly fluid build-up, or edema, according to the University of Florida and the company Air Products. Oxygen must get down to minus 297.3 F (minus 183.0 C) to liquefy, so frostbite would be a problem. If you've ever wondered what swimming in a pool of liquid oxygen would be like, the answer is: very, very cold, according to Carl Zorn of the Thomas Jefferson National Accelerator Facility.

#OXYGEN ATOM FREE#

The outermost shell can hold a total of eight electrons, which explains oxygen's tendency to react with other elements: Its outer shell is incomplete, and electrons are thus free for the taking (and giving). Oxygen has eight total electrons - two orbit the nucleus in the atom's inner shell and six orbit in the outermost shell. The word comes from the Greek 'oxy' and 'genes,' meaning 'acid-forming.' Oxygen's third discoverer was Antoine-Laurent de Lavoisier, a French chemist who gave the element its name. Priestly published his findings in 1774, beating out Swiss scientist Carl Wilhelm Steele, who had actually isolated oxygen in 1771 and written about it, but not published the work. He noted that a candle burned more brightly in this gas, according to the RSC, thanks to oxygen's role in combustion. English chemist and clergyman Joseph Priestly isolated oxygen by shining sunlight on mercuric oxide and collecting the gas from the reaction. The identity of that gas remained a mystery until the 1770s, when three chemists converged on its discovery more or less at the same time. The first inkling humans had of the existence of oxygen as an element was in 1608, when Dutch inventor Cornelius Drebbel reported that the heating of saltpeter (potassium nitrate) released a gas, according to the Royal Society of Chemistry (RSC). Anaerobes that were unable to adapt or survive in the presence of oxygen died off in this new world. The new atmosphere caused a mass extinction of anaerobes, which are organisms that don't require oxygen. Life today depends heavily on oxygen, but the initial build-up of this element in the atmosphere was nothing short of a disaster. These rocks were originally in shallow seas, suggesting that oxygen from photosynthesis first began to accumulate in marine environments about half a billion years before it began to accumulate in the atmosphere around 2.5 billion years ago. Photosynthesis by cyanobacteria was likely ongoing before significant levels of oxygen built up in Earth's atmosphere a March 2014 study published in the journal Nature Geoscience found that 2.95 billion-year-old rocks found in South Africa contained oxides that would have required free oxygen to form.

Oxygen atom