What is Oxygen
Oxygen (pronunciation: OK-si-jen) is a colorless element that belongs to the group of Chalcogens in the periodic table, and it is represented by the chemical symbol O [1, 2, 3]. A highly reactive non-metal, it can easily form oxides with most of the other elements and their compounds . At room temperature, it is an odorless, tasteless diatomic gas characterized by the formula O2 .
Oxygen has three-known stable isotopes, including 16O, 17O, and 18O with a natural abundance of 99.76%, 0.04%, and 0.20% respectively . Radioactive isotopes from 12O to 24O also exist out of which the longest-lived is 15O characterized by a half-life period of 122.24 seconds whereas the shortest-lived 12O has a half-life period of 580(30) X 10-24 seconds .
Where is Oxygen Found
It is found in the Earth’s atmosphere, constituting 21% of the atmospheric volume . Oxygen along with its compounds accounts for nearly two-thirds of the mass of the human body and 49.2% of the mass of the Earth’s crust .
Oxygen gas is commercially extracted by fractional distillation of liquefied air . It can also be obtained by passing dry air through zeolite, a microporous mineral that can absorb nitrogen but leave oxygen . Passing the air through a selectively permeable ceramic membrane can produce highly pure oxygen .
It can artificially be produced in the laboratory by using manganese (IV) oxide as a catalyst to decompose aqueous hydrogen peroxide or by electrolytic decomposition of water . Oxygen is also formed when potassium chlorate (KClO3) is heated strongly .
Origin of its Name: It is derived from ‘oxy genes’, Greek for “acid forming” [1, 2]
Who discovered it: The English chemist Joseph Priestly and the German-Swedish chemist Carl Wilhelm Scheele are known for their independent discovery of oxygen [1, 2].
When and How was it Discovered
Although several chemists had produced oxygen before its discovery, they all failed to identify it and describe its properties . In 1608, the Dutch engineer Cornelius Drebbel showed that heating potassium nitrate (saltpeter) released a gas, which we now know was oxygen .
The credit for the discovery of oxygen can be given to three chemists – Joseph Priestley, Carl Wilhelm Scheele, and Antoine Lavoisier . Having produced oxygen in 1774 in Wiltshire, England by heating mercuric oxide and collecting the gas that was released, Priestley published an account of his discovery . He observed that the gas made breathing easier and caused a candle to burn more brightly .
Although Carl Wilhelm Scheele had successfully obtained oxygen in 1771 in Uppsala, Sweden, his written account got published in 1777 much later than that of Priestley . The French chemist Antoine Lavoisier is known for proposing the name oxy-gene because he incorrectly believed that the new gas was essential to the formation of all acids .
|Atomic number||8 |
|CAS number||7782-44-7 |
|Position in the periodic table||Group||Period||Block|
|16 ||2 ||p |
Properties and Characteristics of Oxygen
|Relative atomic mass||15.999 |
|Atomic mass||15.999 amu |
|Molar mass||15.99940 ± 0.00030 g/mol |
|Molecular weight||31.998 g/mol |
|Mass number||16 |
|Allotropes||O2, O3 |
|Color||Gas: colorless, Liquid: pale blue [1, 8]|
|Melting point/freezing point||-218.79 °C, -361.82 °F |
|Boiling point||-182.962 °C, -297.332 °F |
|Density||0.001308 g cm-3 |
|State of matter at room temperature (solid/liquid/gas)||Gas [1, 7]|
|Thermal (heat) conductivity||0.02658 W/(m K) |
|Specific heat||918 J kg-1 K-1 |
|Bulk modulus||Unknown |
|Shear modulus||Unknown |
|Young’s modulus||Unknown |
|– Temperature (K)||400||600||800||1000||1200||1400||1600||1800||2000||2200||2400|
|– Pressure (Pa)||–||–||–||–||–||–||–||–||–||–||–|
|Oxidation state/Oxidation number||-2, -1, +1, +2 |
|Isotopes||Isotope||Mass||Abundance (%)||Half-life||Mode of decay|
Atomic Data of Oxygen (Element 8)
|Valence electrons||6 |
|– n||2 |
|– ℓ||1 |
|– mℓ||-1 |
|– ms||-1/2 |
|Electron configuration (noble gas configuration)||[He] 2s22p4 |
|– Number of electrons||8 |
|– Number of neutrons||8 |
|– Number of protons||8 |
|Radius of Atom|
|– Atomic radius||1.52 Å |
|– Covalent radius||0.64 Å |
|Electronegativity (Pauling-scale)||3.44 |
|Electron affinity||140.976 kJ mol-1 |
|Ionization energy (kJ mol-1)||1st||2nd||3rd||4th||5th||6th||7th||8th|
- Oxygen gas is commercially used in the steel industry for removing undesirable compounds and impurities during the forging process [1, 12].
- Large amounts of oxygen are used to manufacture various chemicals like hydrogen peroxide and nitric acid . Epoxyethane, a chemical used for producing antifreeze (chemicals added to water in automobile engines) is manufactured from oxygen .
- It can be used for making polyester and chloroethane, which is a precursor to PVC .
- The oxy-acetylene flame used in welding or cutting metals contains oxygen gas .
- It is now increasingly used for treating sewage and industrial effluent .
- Compressed oxygen gas is used in pneumatic tools, including riveters, drills, and paint sprayers .
- It is used in pediatric incubators in hospitals to help provide newborn babies the environmental safety they need when they are born prematurely .
- Rocket fuel has high oxygen content for increasing the burning rate .
- Astronauts, submariners, and scuba divers rely on artificially-delivered oxygen . For deep-sea diving, oxygen is diluted with other gases like helium or nitrogen for preventing oxygen toxicity .
Biological Role of Oxygen
The element first appeared 2 billion years ago when photosynthesis of cyanobacteria resulted in a buildup of oxygen in the Earth’s atmosphere 
Photosynthesis uses solar energy to divide water molecules into hydrogen and oxygen, from which the oxygen accumulates into the atmosphere while hydrogen along with carbon dioxide produces biomass .
Life on Earth now depends on oxygen because all living things need it for respiration and producing energy . Since gaseous oxygen is soluble in water, aerobic bacteria can survive in lakes, rivers, and oceans .
- Oxygen liquefies at -183.0 °C and can cause frostbite after skin contact .
- Its graphical representation indicates its importance and existence in the air, and in combination with hydrogen, in water .
- Too little oxygen (below 17% by volume in the Earth’s atmosphere) can make breathing difficult for people while too much (above 25% in the atmosphere) can cause organic compounds to become highly flammable .
- Oxygen is produced at the center of stars, with nuclear fusion occurring between carbon-12 and helium-4 .
Cost of Oxygen
Canned oxygen usually costs less than $50 per unit . The price of 100 g of pure oxygen is about $0.3 while its price in bulk is $0.02 .
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