Oxygen

Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O ₂. Diatomic oxygen gas currently constitutes 20.95% of the Earth's atmosphere, though this has changed considerably over long periods of time. Oxygen makes up almost half of the Earth's crust in the form of oxides. Many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins, nucleic acids, carbohydrates, and fats, as do the major constituent inorganic compounds of animal shells, teeth, and bone.

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Enjoy It While You Can: Dropping Oxygen Will One Day Suffocate Most Life on Earth

Warming climate spurs harmful oxygen loss in lakes

Earth's Oxygen Came From an Unexpectedly Deep And Hot Source, Study Suggests

Oxygen Evolution Reaction Breakthrough for Efficient Hydrogen Generation

Rapid fluctuations in oxygen levels coincided with Earth's first mass extinction

Looking at oxygen storage dynamics in three-way catalysts

Study: Decreased Global Oxygen Availability Caused End-Ediacaran Mass Extinction

Earth’s First Known Mass Extinction Event Starved Life of Oxygen

Ceramics that breathe oxygen at lower temperatures help us breathe cleaner air

Volcanic activity and low ocean oxygen events linked to climate warming and rapid ice melt during last ice age, study finds

Doctors Warn FDA of Risks Posed by Flawed Oxygen Devices

How do we know when blood oxygen is too low?

Oxygen Might Not Be an Ideal Sign of Life on Other Planets After All

Scientists Discover a New Way Exoplanets Could Make Oxygen; Unfortunately, it Doesn’t Require Life

Earth’s oxygen levels over time could help us spot alien life

How fluctuating oxygen levels may have accelerated animal evolution

System for generating oxygen within cells

New abiotic pathway for the formation of oxygen

Study uncovers mechanisms of reactive oxygen species in stem cell function and inflammation prevention

A smartphone's camera and flash could help people measure blood oxygen levels at home