It is a chemical element that has an atomic number 8. There are eight electrons, eight protons and eight neutrons in an electrically neutral atom. It has a symbol ''O'' and a member of group 16 of the periodic table. It is in Period 2 and a P-block element. It has two electrons in K-shell and six in L-shell. The standard atomic weight of oxygen is 15.99 amu. It is a highly reactive and oxidizing agent forming Oxides. It is non-metal and has a light blue colour in liquid and solid states. In the gaseous phase, it is colourless. The electronic configuration of Oxygen is 1s2, 2s2, 2p4. The electronegativity of Oxygen is 3.44 while its Oxidation states can be −2, −1, 0, +1, +2 depending on the bonding atom' electronegativity.There are three stable isotopes of Oxygen which are Oxygen-16, Oxygen-17, and Oxygen-18. The abundance of oxygen-16 is 99.76%, Oxygen-17 is 0.04% and Oxygen-18 is 0.20%. At standard temperature and pressure, it is a gas but when the temperature is decreased to  90.188 K ?(−182.962 °C, ?−297.332 °F) it turns into liquid. While decreasing temperature further to 54.36 K ?(−218.79 °C, ?−361.82 °F) it turns into solid.

Micha? S?dziwój, Carl Wilhelm Scheele and Joseph Priestley are credited for its discovery.  Diatomic oxygen is the most abundant gas constitutes 20.95% of the Earth's atmosphere. The second most abundant after diatomic nitrogen. About half (49.2%) of the Earth's crust is made of oxygen in the form of oxides. Earth is the only planet in the solar system which has more oxygen by far than any other planet. It can be found in the Sun making 0.9% of its mass.

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What is oxygen saturation?

It is the measure of the concentration of oxygen dissolved or in a medium to be dissolved. It can be measure in a medium through an oxygen sensor or optrode (optical sensor device).

In medicine,  Oxygen situation is when oxygen combines with blood in the tissues and oxygenate it. In environmental science it the amount of oxygen dissolved in water in percentage.


Who discovered oxygen?

Three scientists are credited for this discovery,  Michael Sendivogius, Carl Wilhelm Scheele and Joseph Priestley. Polish alchemist, physician, and philosopher, Michael Sendivogius describe it in his work as  'cibus vitae' (food of life)  in 1604. He recovered it as a byproduct of the thermal decomposition of potassium nitrate. The Swedish scientist Carl Wilhelm Scheele is also credited for the discovery of oxygen. He produced it by heating Mercuric oxide. It is described in his work titled 'Treatise on Air and Fire' as ''fire air''.His work was published in 1777. Joseph Priestley a British scientist obtained it by focusing sunlight on a tube filled with Mercuric oxide. He named this gas "dephlogisticated air". Joseph Priestley noted that a burning candle burns brighter when this gas is released and a mouse was more active when breathing this gas. He published his finding in 1775 in a paper titled "An Account of Further Discoveries in Air",

Later on Frenc chemist Antoine Laurent Lavoisier claimed that he had discovered a new substance. In October 1774 Priestley visited him. And told him how he separated the new gas. So, in the discovery of Oxygen Joseph Priestley is given the priority usually.