Oxygen
Oxygen is the third most abundant chemical element in the universe, trailing only hydrogen and helium. About 0.9% of the Sun's mass consists of oxygen. This element forms approximately half of Earth's crust by weight as various oxides including silicon dioxide, iron oxides, and silicates. The world's oceans contain 88.8% oxygen by mass within water molecules. Mars possesses just 0.1% oxygen gas by volume while Venus has even less than that amount. Earth remains unusual among Solar System planets for maintaining such high concentrations of free diatomic elemental oxygen in its atmosphere.
Philo of Byzantium conducted one of the first known experiments on combustion and air during the second century before the common era. He inverted a vessel over a burning candle and surrounded the neck with water to observe rising liquid levels. Philo incorrectly surmised that parts of the air converted into fire escaped through glass pores. Michael Sendivogius wrote Twelve Treatises on the Philosopher's Stone in 1604 describing a substance he called food of life. Sendivogius performed experiments between 1598 and 1604 recognizing this substance equaled gaseous byproducts from potassium nitrate decomposition. Carl Wilhelm Scheele produced oxygen around 1770-1775 but did not publish until years later due to phlogiston theory constraints. Joseph Priestley liberated dephlogisticated air on the 1st of August 1774 using sunlight focused on mercuric oxide.
Antoine Lavoisier conducted quantitative experiments starting in 1774 to discredit phlogiston theory completely. He observed no overall weight increase when heating tin and air inside closed containers. Air rushed back in upon opening the container indicating consumed trapped air portions. Tin gained weight matching exactly the mass of incoming air. Lavoisier published these findings in 1777 proving air contained two gases: vital air essential for combustion and azote meaning lifeless which supported neither process. Nitrogen retained its French name while English adopted nitrogen instead. Lavoisier renamed vital air to oxygen derived from Greek roots acid sharp plus producer begetter because he mistakenly believed all acids contained oxygen. Sir Humphry Davy determined chemists were wrong about this belief in 1812 though the name remained established.
Dioxygen molecules contain two unpaired electrons creating a spin triplet state called triplet oxygen. This configuration prevents spontaneous combustion with most organic molecules possessing paired electron spins. Liquid oxygen demonstrates paramagnetism allowing bridges to support against gravity between powerful magnet poles. Singlet oxygen represents higher energy species where all electron spins pair together making it much more reactive than normal molecular oxygen. Trioxygen known as ozone absorbs strongly ultraviolet radiation forming protective layers above Earth's surface. Tetraoxygen discovered in 2001 exists under extreme pressure conditions exceeding twenty gigapascals. Metallic phases appear when solid oxygen subjected pressures surpass ninety-six gigapascals becoming superconducting at very low temperatures.
The Great Oxygenation Event began approximately 2.45 billion years ago during the Neoarchean-Paleoproterozoic boundary. Marine photoautotrophs like cyanobacteria provide roughly seventy percent of free oxygen produced on Earth today. Plants generate the remaining thirty percent through terrestrial photosynthesis processes. An adult human inhales 1.8 to 2.4 grams of oxygen per minute while resting. Humanity collectively breathes over six billion tonnes annually according to current population estimates. Photosynthesis releases oxygen into atmospheres while respiration decay and combustion remove it continuously. Oxygen levels trend slightly downward globally possibly due to fossil fuel burning activities. Polar oceans support higher life densities because cold water holds twice as much dissolved oxygen compared to warmer tropical regions.
One hundred million tonnes of oxygen extract from air every year for industrial applications worldwide. Fractional distillation of liquefied air remains the most common extraction method producing vaporized oxygen leaving liquid nitrogen behind. Pressure swing adsorption passes clean dry air through zeolite molecular sieves absorbing nitrogen delivering gas streams containing ninety to ninety-three percent oxygen. German engineer Carl von Linde developed commercially viable liquid oxygen production independently in 1895 alongside British engineer William Hampson. Both men lowered temperatures until air liquefied then distilled components boiling off separately capturing them individually. Robert H. Goddard successfully flew a small liquid-fueled rocket fifty-six meters at ninety-seven kilometers per hour on the 16th of March 1926 using gasoline fuel and liquid oxygen oxidizer in Auburn Massachusetts.
Oxygen therapy treats emphysema pneumonia congestive heart failure disorders increasing pulmonary artery pressure impairing body uptake abilities. Hyperbaric medicine uses special chambers increasing partial pressures around patients treating carbon monoxide poisoning gas gangrene decompression sickness bends. Decompression bubbles form when divers ascend too quickly resulting inert gases mostly nitrogen helium dissolving back into blood under increased pressure. Modern space suits surround occupants with nearly pure oxygen at one-third normal pressure maintaining normal blood partial pressures while preserving suit flexibility. Submarines operate atmospheric diving suits breathing air scrubbed of carbon dioxide replacing oxygen maintaining constant partial pressures. Pressurized commercial airplanes automatically supply emergency oxygen masks activating chemical generators forcing iron filings sodium chlorate inside canisters producing steady streams exothermic reactions during cabin depressurization events.
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Common questions
What is the abundance of oxygen in the universe and Earth's crust?
Oxygen is the third most abundant chemical element in the universe trailing only hydrogen and helium. This element forms approximately half of Earth's crust by weight as various oxides including silicon dioxide iron oxides and silicates.
Who discovered oxygen and when did Joseph Priestley liberate dephlogisticated air?
Joseph Priestley liberated dephlogisticated air on the 1st of August 1774 using sunlight focused on mercuric oxide. Carl Wilhelm Scheele produced oxygen around 1770-1775 but did not publish until years later due to phlogiston theory constraints.
Why did Antoine Lavoisier rename vital air to oxygen and when was this belief corrected?
Antoine Lavoisier renamed vital air to oxygen derived from Greek roots acid sharp plus producer begetter because he mistakenly believed all acids contained oxygen. Sir Humphry Davy determined chemists were wrong about this belief in 1812 though the name remained established.
When did the Great Oxygenation Event begin and what percentage of free oxygen comes from marine photoautotrophs?
The Great Oxygenation Event began approximately 2.45 billion years ago during the Neoarchean-Paleoproterozoic boundary. Marine photoautotrophs like cyanobacteria provide roughly seventy percent of free oxygen produced on Earth today.
How is oxygen extracted for industrial applications and who developed commercially viable liquid oxygen production?
Fractional distillation of liquefied air remains the most common extraction method producing vaporized oxygen leaving liquid nitrogen behind. German engineer Carl von Linde developed commercially viable liquid oxygen production independently in 1895 alongside British engineer William Hampson.