Oxygen

<---Nitrogen       Fluorine--->

• Symbol: O

• Atomic Number: 8

• Atomic Weight: 15.999

• Classification: Gas and nonmetal

• Phase at Room Temperature: Gas

• Density: 1.429 g/L

• Melting Point: -218.79°C, -361.82°F

• Boiling Point: -182.95°C, -297.31°F

• Discovered by: Joseph Priestley in 1774 and C. W. Scheele independently in 1772

Oxygen is an important element that is needed by most life forms on Earth to survive. It is the third most abundant element in the universe and the most abundant element in the human body. Oxygen has 8 electrons and 8 protons. It is located at the top of column 16 in the periodic table.

The oxygen cycle plays an important role in life on Earth. Click here to read more about the oxygen cycle.

Characteristics and Properties

Under standard conditions oxygen forms a gas that is composed of molecules consisting of two oxygen atoms (O2). This is called a diatomic gas. In this form oxygen is a colorless, odorless, tasteless gas.

Oxygen also exists as the allotrope ozone (O3). Ozone exists in the upper region of the Earth's atmosphere forming the ozone layer which helps to protect us from the harmful rays of the sun.

Oxygen is a very reactive element in its pure state and can make compounds from many other elements. Oxygen readily dissolves in water.

Where is oxygen found on Earth?

Oxygen is found all around us. It is one of the most important elements on planet Earth. Oxygen makes up around 21% of the Earth's atmosphere and 50% of the mass of the Earth's crust. Oxygen is one of the atoms that makes up water (H2O).

Oxygen is an important element to life on Earth. It is the most abundant element in the human body making up around 65% of the body's mass.

How is oxygen used today?

Oxygen is used by animals and plants in the respiration (breathing) process. Tanks of oxygen are used in medicine to treat people with breathing problems. They are also used as life support for astronauts and scuba divers.

The majority of the oxygen used in industry is used in the manufacturing of steel. Other applications include making new compounds such as plastics and creating a very hot flame for welding. Liquid oxygen is combined with liquid hydrogen to make rocket fuel.

How was it discovered?

Swedish chemist C. W. Scheele first discovered oxygen in 1772. He called the gas "fire air" because it was needed for fire to burn. Scheele did not publish his results right away and the element was independently discovered by British scientist Joseph Priestley in 1774.

Where did oxygen get its name?

The name oxygen comes from the Greek word "oxygenes" meaning "acid producer". It was called this because early chemists thought that oxygen was necessary for all acids.

Isotopes

There are three stable isotopes of oxygen. Over 99% of stable oxygen is made up of the isotope oxygen-16.

Interesting Facts about Oxygen

• Oxygen dissolves in cool water easier than in warm water.

• Water can be converted into hydrogen and oxygen through electrolysis.

• The oxygen that is found in the air is produced by photosynthesis. Without plants, there would be very little oxygen in the air.

• In the solar system, only the Earth has a high percentage of oxygen.

• Oxygen atoms make up an essential part of proteins and DNA in our bodies.

• The process of oxygen combining with other atoms to make compounds is called oxidation.