Oxygen is a colorless, odorless gas with the chemical formula O₂, consisting of two oxygen atoms connected by a double bond. First isolated by Carl Wilhelm Scheele in 1772 and independently by Joseph Priestley in 1774, oxygen makes up 21% of Earth’s atmosphere and is the third most abundant element in the universe. This highly reactive gas is the cornerstone of life as we know it – enabling cellular respiration in most organisms while simultaneously posing the paradox of slowly destroying the very cells it keeps alive through oxidative stress. From the Great Oxidation Event 2.4 billion years ago that transformed Earth’s atmosphere and enabled complex life, to its modern roles in medicine, industry, and space exploration, oxygen remains one of the most vital yet dangerous elements we interact with daily.

Find a review of the 50 most important industrial gases here.

20 Fun Facts About Oxygen

Beyond the basics above, what else should we know about Oxygen? Check out the 20 fun facts below!

1. Liquid oxygen is pale blue and magnetic, defying gravity by bridging between the poles of a strong magnet.
2. Earth’s oxygen took 2 billion years to accumulate, with early oxygen poisoning and killing most existing anaerobic life forms.
3. The double bond in O₂ contains two unpaired electrons, making it paramagnetic – unique among common atmospheric gases.
4. Pure oxygen accelerates aging – mice in 100% oxygen live only 3 days due to overwhelming oxidative damage.
5. Oxygen becomes a metallic superconductor at 96 GPa pressure, glowing dark red before transforming completely.
6. The Amazon rainforest consumes all the oxygen it produces; ocean phytoplankton provide 50-80% of breathable oxygen.
7. Oxygen therapy above 2.5 atmospheres causes seizures as the brain becomes overwhelmed by reactive oxygen species.
8. The element has exactly three stable isotopes (¹⁶O, ¹⁷O, ¹⁸O) used to track ancient climate through ice cores.
9. Fireflies use oxygen so efficiently in bioluminescence that their light production is 96% energy efficient.
10. Oxygen dissolves 10 times better in cold water, explaining why polar oceans support more life than tropical seas.
11. The gas liquefies at -183°C, cold enough to make rubber as brittle as glass and shatter on impact.
12. Apollo 1 astronauts died in pure oxygen at 16.7 PSI – creating fire conditions impossible in normal air.
13. Oxygen molecules collide 10 billion times per second at room temperature but rarely react due to spin restrictions.
14. Earth uniquely has free oxygen – all other known planets have oxygen only in compounds like CO₂ or water.
15. The “oxygen catastrophe” 2.4 billion years ago created the first mass extinction, but enabled the ozone layer.
16. Mountaineers above 8,000m enter the “death zone” where oxygen partial pressure can’t sustain human life indefinitely.
17. Oxygen-18 in fossils reveals dinosaurs’ body temperatures were 5-10°C warmer than modern reptiles.
18. Industrial oxygen production consumes 1% of all electricity worldwide through air separation plants.
19. Singlet oxygen (excited O₂) glows red and is 1,000 times more reactive, used in cancer photodynamic therapy.
20. The element forms more compounds than any other except hydrogen – from rust to DNA, oxygen bonds dominate chemistry.

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