Oxygen

Oxygen is a very important chemical element. It is a member of the chalcogen group in the periodic table.

This element is highly reactive. This means it loves to bond with other things. It forms oxides with most elements. Oxygen is the most abundant element in the Earth's crust. It makes up almost half of the crust. You can find it in water and carbon dioxide. It is also in iron oxides and silicates.

In space, it is the third-most abundant element. Only hydrogen and helium are more common.

Most oxygen in our air is a gas called dioxygen.

Two oxygen atoms bind together to form this gas. It has no color and no smell. This gas makes up about 20.95% of our atmosphere. There is also a rarer form called ozone.

Ozone forms a protective layer in the stratosphere. This layer shields life from harmful ultraviolet radiation. However, ozone at the surface is an air pollutant. It is a corrosive byproduct of smog. Living things use oxygen for cellular respiration.

This is a way to get stored energy from food. During this, oxygen reacts with organic molecules. This process releases carbon dioxide as a waste product.

Many people helped us understand oxygen over many centuries.

Michael Sendivogius described a substance in the air before 1604. He called it the "food of life." Later, Carl Wilhelm Scheele produced oxygen in 1771. Joseph Priestley also discovered it in 1774. Priestley was the first to publish his findings. He called the gas "dephlogisticated air." He did not know it was a real element.

Antoine Lavoisier was the first to recognize it as an element. He did this in 1777. He also explained how it works in combustion.

Scientists used to believe in the phlogiston theory. This theory said things burned by losing a substance called phlogiston.

Lavoisier proved this was wrong with careful experiments. He heated tin in a closed container. He saw the tin increased in weight. This happened because it took oxygen from the air.

Lavoisier named the element oxygen in 1777. He used Greek roots meaning "acid producer." He thought oxygen was in all acids. He was actually wrong about that part. But the name stuck and we still use it today.

We use oxygen for many important jobs in our world.

Factories use it to make steel, plastics, and textiles. It is used in welding and cutting metals. Oxygen is also used as rocket propellant.

Doctors use oxygen therapy to help people breathe. It is also used in life-support systems. These systems are needed for aircraft and submarines. Divers and astronauts also need it to survive. Oxygen is truly a part of almost everything we do.