Take in … breath out. Oxygen forever, the component that keeps a lot of life on Earth murmuring.
Component No. 8 on the Periodic Table of the Elements is a boring gas that makes up 21% of Earth's air. Since it's overall, oxygen is not difficult to excuse as dull and latent; truth be told, it's the most responsive of the non-metallic components.
Earth has been oxygenated for around 2.3 billion to 2.4 billion years, and levels started to crawl up at minimum 2.5 billion years prior. Nobody knows very why this lung-accommodating gas unexpectedly turned into a critical piece of the climate, yet it's conceivable that geologic changes on Earth prompted oxygen created by photosynthesizing organic entities staying close by, rather than being consumed in geologic responses, as per the review analysts.
Just the facts
Atomic Number (number of protons in the nucleus): 8
Atomic Symbol (on the Periodic Table of Elements): O
Atomic Weight (average mass of the atom): 15.9994
Density: 0.001429 grams per cubic centimeter
Phase at Room Temperature: Gas
Melting Point: minus 361.82 degrees Fahrenheit (minus 218.79 degrees Celsius)
Boiling Point: minus 297.31 degrees F (minus 182.95 degrees C)
Number of isotopes (atoms of the same element with a different number of neutrons): 11; three stable
Most common isotopes: O-16 (99.757 percent natural abundance).
Breath of Life
Oxygen is the third most abundant element in the universe. Cyanobacteria, which are organisms that "breathe" using photosynthesis, take in carbon dioxide and exhale oxygen, just like modern plants. Cyanobacteria were likely responsible for the first oxygen on Earth, an event grandly known as the Great Oxidation Event.
Photosynthesis by cyanobacteria was probable progressing before huge degrees of oxygen developed in Earth's climate; the diary Nature Geoscience found that 2.95 billion-year-old rocks found in South Africa contained oxides that would have required free oxygen to frame. These stones were initially in shallow oceans, recommending that oxygen from photosynthesis initially started to gather in marine conditions about a large portion of a billion years before it started to amass in the environment around 2.5 billion years prior.
Life today depends heavily on oxygen, but the initial build-up of this element in the atmosphere was nothing short of a disaster. The new atmosphere caused a mass extinction of anaerobes, which are organisms that don't require oxygen. Anaerobes that we're unable to adapt or survive in the presence of oxygen died off in this new world. [Infographic: Earth's Atmosphere Top to Bottom]
Fast forward — way forward. The first inkling humans had of the existence of oxygen as an element was in 1608. The heating of the saltpeter (potassium nitrate) released a gas. 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. English chemist and clergyman Joseph Priestly isolated oxygen by shining sunlight on mercuric oxide and collecting the gas from the reaction. He noted that a candle burned more brightly in this gas.
Oxygen has eight total electrons — two orbits of nucleus in the atom's inner shell and six orbits in the outermost shell. 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.
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