|colorless gas; light blue liquid.|
Light reflection lines of oxygen
|Name, symbol, number||oxygen, O, 8|
|Pronunciation||/[invalid input: 'ɨ']/ OK-si-jən|
|Element category||nonmetal, chalcogen|
|Group, period, block||16, 2, p|
|Standard atomic weight||15.999(1) g/mol|
|Electron configuration||[He] 2s2 2p4|
|Electrons per shell||2, 6 (Image)|
|Density||(0 °C, 101.325 kPa)|
|Liquid density at b.p.||1.141 g/cm3|
|Melting point||54.36 K, -218.79 °C, -361.82 °F|
|Boiling point||90.20 K, -182.95 °C, -297.31 °F|
|Critical point||154.59 K, 5.043 MPa|
|Heat of fusion||(O2) 0.444 kJ/mol|
|Heat of vaporization||(O2) 6.82 kJ/mol|
|Specific heat capacity||(25 °C) (O2)|
|Oxidation states||2, 1, −1, −2|
|Electronegativity||3.44 (Pauling scale)|
||1st: 1313.9 kJ/mol|
|2nd: 3388.3 kJ/mol|
|3rd: 5300.5 kJ/mol|
|Covalent radius||66±2 pm|
|Van der Waals radius||152 pm|
|Thermal conductivity||(300 K) 26.58x10-3 W/(m·K)|
|Speed of sound||(gas, 27 °C) 330 m/s|
|CAS registry number||7782-44-7|
|Most stable isotopes|
|Main article: Isotopes of oxygen|
Oxygen (O) is a chemical element. In nature, oxygen is a gas with no color or smell. Oxygen is a very important element because we need it to live. It is a part of the air people breathe and the water people drink. Many living things (including humans) need oxygen to live and breathe, though it is poisonous to some forms of life. In liquid state of matter, oxygen is light blue.
Discovery of oxygen[change | change source]
Oxygen was initially discovered in 1772 by Carl Wilhelm Scheele. Then Joseph Priestley also discovered it two years later and spread the news before Scheele. This made many people think that Priestley discovered oxygen first. The word oxygen comes from Greek words: oxus (acid) and gennan (generate). Oxygen comes to earth from all parts of the universe in meteorites. It is also found in minerals and plants that grow on the earth and other planets.
Oxygen in nature[change | change source]
Air also contains oxygen. Air is made of many gases that are mixed together. Approximately 21% of the air is oxygen. Oxygen is especially important because all animals use oxygen to get energy from their food.
Uses of oxygen[change | change source]
Oxygen is what makes burning possible. This is called combustion. When an object or something burns, oxygen combines with another substance and releases heat and light. For instance, when wood burns, the oxygen in air combines with the wood to create fire. This ability of oxygen has many uses. But it also makes pure oxygen very dangerous. If pure oxygen touches a flame or spark, it can make a hot fire and cause great damage. Combustion is used in many ways.
- When oxygen is mixed with acetylene, it can create a very hot flame. This is used in welding, of metals.
- Liquid oxygen can make a hot flame with other propellants for rocket engines.
- Oxygen can be used in smelting metal from ore.
- Oxygen is used in hospitals for killing bacteria. It is also used when a patient has had carbon monoxide poisoning.
- Oxygen is used in water treatment to purify the water to make it safe to drink.
- People with certain illnesses are less sick when they breathe pure oxygen.
Production of gas[change | change source]
Pure oxygen can be produced in several ways. In nature, plants produce oxygen by using sunlight, carbon dioxide (another gas) and water. This process is called photosynthesis. Most of the oxygen in the air is produced by photosynthesis.
People mostly get pure oxygen from air by separating it from nitrogen. Oxygen can also be produced by electrolysis. In this process, electricity passes through water. As a result, the water molecules break and release oxygen and hydrogen gas.
References[change | change source]
- "Liquid Oxygen Page". allatoms.com. 2003 [last update]. Retrieved 22 May 2012. Check date values in:
- "Oxygen Facts - Periodic Table of the Chemical Elements". about.com. Retrieved 22 May 2012. Text "year] " ignored (help)
- "Lox/LH2". astronautix.com. 2011 [last update]. Retrieved 22 May 2012. Check date values in: