What Is Oxygen?
QUICK ANSWER
Oxygen is a chemical element with atomic number 8 and the symbol O. It is a colorless, odorless gas at room temperature that makes up about 21% of Earth's atmosphere and is essential for almost all life. Most organisms need oxygen to convert food into energy.
Oxygen is the third most abundant element in the universe and probably the most familiar to most people. Every breath you take is mostly nitrogen with a critical portion of oxygen that your body uses to convert food into energy. From combustion to respiration to rust, oxygen drives many of the chemical reactions that shape the world around us.
Where is oxygen on the periodic table?
Oxygen has atomic number 8, the symbol O, and sits in group 16 of the periodic table, called the chalcogens. Its atomic mass is about 16, made up of 8 protons and usually 8 neutrons. Oxygen is a non-metal that exists naturally as a diatomic molecule (O₂) in the air. Three stable isotopes exist: O-16 makes up about 99.76%, with O-17 and O-18 making up the rest. The element was discovered independently by Carl Wilhelm Scheele around 1772 and Joseph Priestley in 1774, with Antoine Lavoisier naming it a few years later.
What are the properties of oxygen?
At room temperature, oxygen is a colorless, odorless, tasteless gas. It liquefies at -183°C (-297°F) into a pale blue liquid and freezes at -218°C (-361°F) into pale blue crystals. Oxygen is highly reactive, readily combining with most other elements through oxidation reactions. It is paramagnetic, meaning liquid oxygen is weakly attracted to magnets. Pure oxygen does not burn itself, but it dramatically accelerates the burning of other materials, which is why oxygen tanks require careful handling around any source of ignition or sparks.
What is oxygen used for?
Oxygen has enormous industrial and medical uses. Steelmaking consumes about 55% of industrial oxygen, where it is blown through molten iron to remove impurities. Medical oxygen is essential for patients with breathing difficulties, surgery, and respiratory conditions. Welding and cutting torches use oxygen to produce extremely hot flames. Rocket engines use liquid oxygen as an oxidizer for liquid fuels. Wastewater treatment uses oxygen to support beneficial bacteria. Oxygen is also used to make many chemicals, including ethylene oxide for plastics and propylene oxide for foams.
Why is oxygen essential to life?
Most life on Earth uses oxygen for cellular respiration, the process that converts food into ATP, the energy currency of cells. Mitochondria in animal cells use oxygen to oxidize glucose, producing carbon dioxide and water as waste. Without oxygen, this energy-yielding process cannot work, which is why most animals and plants cannot survive more than a few minutes without it. Plants produce oxygen through photosynthesis, splitting water molecules and releasing O₂ as a byproduct, which is what created the oxygen-rich atmosphere that allowed complex life to evolve.
Oxygen is everywhere in modern life, from the air you breathe to the steel in your car to the oxygen tank in a hospital. It is one of the most studied and most used elements on the periodic table, and Earth would be unrecognizable without it.
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