50 Fun Facts About Oxygen

What is oxygen's atomic number?

Its symbol is O and it belongs to the chalcogen group of the periodic table.

Roughly what fraction of Earth's atmosphere is oxygen gas, by volume?

Nitrogen makes up most of the rest; the oxygen figure has swung a great deal over geological time.

Oxygen is the most abundant element in which part of the Earth?

It makes up 49.2% of the crust by mass, locked in oxides such as silica and iron oxide.

Oxygen ranks where in abundance in the universe?

Only hydrogen and helium are more common; about 0.9% of the Sun's mass is oxygen.

What is the chemical formula of ozone?

This reactive allotrope absorbs UVB and UVC in the stratosphere but is a corrosive pollutant at ground level.

Ozone is produced in the upper atmosphere when O2 combines with what?

At low Earth orbit there is enough atomic oxygen to corrode spacecraft.

Priestley is usually given priority over Scheele for discovering oxygen. Why?

Scheele had made the gas by 1773 or earlier in Uppsala, but sat on the results; Priestley published in 1775.

What did Priestley call the gas he liberated from mercuric oxide in 1774?

He noticed candles burned brighter in it and that a mouse lived longer; breathing it himself, he felt 'peculiarly light and easy'.

Scheele published in 1777 and gave the gas what name?

He had made it by heating mercuric oxide and nitrates in 1771-72 but sat on the results because they clashed with phlogiston theory.

Which Polish alchemist isolated oxygen before 1604 and called it 'cibus vitae', the food of life?

He recognised it as the gas released when potassium nitrate decomposes, but contemporaries like Boyle missed the point.

Who first recognised oxygen as an element and correctly explained its role in combustion, in 1777?

His quantitative experiments with tin in a sealed container demolished the phlogiston theory.

Lavoisier's name 'oxygene' comes from Greek roots meaning what?

He wrongly believed every acid contained it; Humphry Davy showed in 1812 that hydrogen chloride does not, but the name stuck.

A poem titled 'Oxygen' in The Botanic Garden (1791) helped the word enter English. Who wrote it?

Charles Darwin's grandfather championed the French name over English objections.

What did Lavoisier call the part of air that supports neither combustion nor respiration?

From the Greek for 'lifeless', it became nitrogen in English but kept the old name in French.

John Dalton assumed water was HO, so he thought oxygen's atomic mass was how many times hydrogen's?

Gay-Lussac and Humboldt showed in 1805 that water is two volumes of hydrogen to one of oxygen, and Avogadro sorted out the rest by 1811.

Which two Polish scientists first liquefied oxygen in a stable state, in March 1883?

Pictet and Cailletet had each made a few drops in December 1877, too little to study.

Who flew the first liquid-fuelled rocket in 1926, burning gasoline with liquid oxygen?

It flew 56 metres at 97 km/h from a field in Auburn, Massachusetts.

What colour are liquid and solid oxygen?

The tint comes from absorption in the red, unlike the sky's blue, which is Rayleigh scattering.

Liquid oxygen can be held between the poles of a strong magnet because it is what?

The unpaired electrons in triplet O2 give it magnetic character, exploited in paramagnetic oxygen analysers.

At roughly what temperature does oxygen condense to a liquid?

That is about -183 C; it freezes at about 54 K.

Why does normal 'triplet' oxygen react only slowly with most organic molecules?

This quirk is what prevents spontaneous combustion of everything around us.

How many stable isotopes does oxygen have?

Oxygen-16 dominates at 99.76%; the ratio of oxygen-18 to oxygen-16 in shells and ice cores reveals ancient climates.

Paleoclimatologists read past temperatures from the ratio of oxygen-18 to oxygen-16 in what?

Lighter oxygen-16 water evaporates faster, so cold periods leave seawater and shells richer in oxygen-18.

Which crashed spacecraft returned solar-wind samples showing the Sun has more oxygen-16 than Earth?

The result implies some unknown process stripped oxygen-16 from the disc of material that formed Earth.

What process produces the free oxygen in Earth's atmosphere?

Marine algae and cyanobacteria may provide around 70% of it; without constant replenishment the reactive gas would vanish from the air.

Oxygen began accumulating in the atmosphere about 2.45 billion years ago in an episode known as what?

Levels stayed below 10% of today's; a second rise around 500 million years ago pushed them to modern values.

Which molecule in red blood cells binds O2, turning from bluish red to bright red?

Molluscs use hemocyanin and spiders and lobsters use hemerythrin instead; a litre of blood can carry up to 200 cm3 of O2.

Roughly how much oxygen does a resting adult inhale per minute?

Across humanity that adds up to more than 6 billion tonnes a year.

Which industry consumes 55% of commercially produced oxygen?

O2 is lanced into molten iron to burn off sulfur and excess carbon, pushing temperatures to 1,700 C.

Ethylene reacted with oxygen gives ethylene oxide, which becomes ethylene glycol, the feedstock for what?

The chemical industry as a whole takes about 25% of commercial oxygen.

What is the most common industrial method for extracting oxygen from air?

About 100 million tonnes a year are made this way; zeolite sieves using pressure swing adsorption are the main alternative.

One litre of liquid oxygen expands to roughly how many litres of gas at room conditions?

That is why hospitals keep bulk liquid tanks outside and warm the liquid through heat exchangers.

Pulling an airliner oxygen mask forces iron filings into which chemical to start the flow?

The exothermic reaction in the chemical generator above each seat produces a steady stream of gas.

Modern space suits use nearly pure oxygen at about what fraction of normal pressure?

The trade-off keeps the suit flexible while giving the blood a normal oxygen partial pressure.

Why did the 1967 Apollo 1 fire spread so quickly?

An electrical surge under a seat, probably from chafed wires, provided the spark.

Breathing 100% oxygen becomes acutely toxic for a diver at only about what depth?

The same seizure risk from ordinary 21% air kicks in at 66 metres or more.

Premature babies were once kept in oxygen-rich incubators until it was found the practice caused what?

Oxygen toxicity generally begins above a partial pressure of about 50 kPa, roughly 50% oxygen at sea level.

Hyperbaric oxygen chambers are used to treat which diving injury?

Raising the O2 pressure helps redissolve inert-gas bubbles; the therapy also treats carbon monoxide poisoning and gas gangrene.

Which two moons of Jupiter have thin oxygen atmospheres, thought to come from water split by radiation?

In astrobiology, oxygen is considered the strongest biosignature, though it can also form without life.

Oxygen dissolves better in cold water. What consequence does this have for the oceans?

About twice as much O2 dissolves at 0 C as at 20 C.

What is the oxidation state of oxygen in almost all of its compounds?

Peroxides are the main exception at -1; oxygen difluoride reaches +2.

Which metastable oxygen molecule, discovered in 2001, was later shown to form an O8 cluster under pressure?

The cluster could be a more powerful oxidiser than O2 or O3, with rocket-fuel potential; a metallic phase forms above 96 GPa.

Which is the most stable radioactive isotope of oxygen, with a half-life of about 122 seconds?

Fifteen radioisotopes are known, and most survive less than 83 milliseconds.

Which English chemist called the part of air needed for fire 'spiritus nitroaereus' in the 1660s?

A mouse or a candle in a closed jar over water used up about one-fourteenth of the air's volume before expiring.

Which 13th-century physician correctly described the oxygenation of blood in the circulatory system?

Michael Servetus rediscovered the idea in 1553, but his books were systematically destroyed.

Oxygen bars, offering higher-than-normal O2 for a fee, first appeared in which country in the late 1990s?

Any performance boost for athletes sucking oxygen on the sidelines is more likely placebo, studies suggest.

Which 2nd-century BCE Greek writer on mechanics studied combustion with an inverted vessel over a candle?

He wrongly concluded that part of the air turned into the element fire and escaped through the glass.

Which two scientists showed in 1805 that water forms from two volumes of hydrogen and one of oxygen?

By 1811 Avogadro had the correct interpretation, fixing Dalton's HO error.

Which French siblings commercialised oxygen production from 1886 using a reversible barium oxide reaction?

Their process lasted until 1906, when fractional distillation of air took over.

Oxyacetylene welding was first demonstrated in which year?

Carl von Linde and William Hampson had independently developed commercial liquid-oxygen processes in 1895.