Oxygen
Atomic Number: 8
Atomic Weight: 15.9994
Melting Point: 54.36 K (-218.79°C or -361.82°F)
Boiling Point: 90.20 K (-182.95°C or -297.31°F)
Density: 0.001429 grams per cubic centimeter
Phase at Room Temperature: Gas
Element Classification: Non-metal
Period Number: 2 Group Number: 16 Group Name: Chalcogen
What's in a name? From the greek words oxys and genes, which together mean "acid forming."
Say what? Oxygen is pronounced as OK-si-jen.
History and Uses:
Oxygen had been produced by several chemists prior to its discovery in 1774, but they failed to recognize it as a distinct element. Joseph Priestley and Carl Wilhelm Scheele both independently discovered oxygen, but Priestly is usually given credit for the discovery. They were both able to produce oxygen by heating mercuric oxide (HgO). Priestley called the gas produced in his experiments 'dephlogisticated air' and Scheele called his 'fire air'. The name oxygen was created by Antoine Lavoisier who incorrectly believed that oxygen was necessary to form all acids.
Oxygen is the third most abundant element in the universe and makes up nearly 21% of the earth's atmosphere. Oxygen accounts for nearly half of the mass of the earth's crust, two thirds of the mass of the human body and nine tenths of the mass of water. Large amounts of oxygen can be extracted from liquefied air through a process known as fractional distillation. Oxygen can also be produced through the electrolysis of water or by heating potassium chlorate (KClO3).
Oxygen is a highly reactive element and is capable of combining with most other elements. It is required by most living organisms and for most forms of combustion. Impurities in molten pig iron are burned away with streams of high pressure oxygen to produce steel. Oxygen can also be combined with acetylene (C2H2) to produce an extremely hot flame used for welding. Liquid oxygen, when combined with liquid hydrogen, makes an excellent rocket fuel. Ozone (O3) forms a thin, protective layer around the earth that shields the surface from the sun's ultraviolet radiation. Oxygen is also a component of hundreds of thousands of organic compounds.
Estimated Crustal Abundance: 4.61×105 milligrams per kilogram
Estimated Oceanic Abundance: 8.57×105 milligrams per liter
Number of Stable Isotopes: 3
Ionization Energy: 13.618 eV
Oxidation States: -2
1s2
2s2 2p4
Breathe in … breathe out. Ahh. Hooray for oxygen, the element that keeps much of life on Earth humming
Just the Facts
- Atomic Number (number of protons in the nucleus): 8
- Atomic Symbol (on the Periodic Table of Elements): O
- Atomic Weight (average mass of the atom): 15.9994
- Density: 0.001429 grams per cubic centimeter
- Phase at Room Temperature: Gas
- Melting Point: minus 361.82 degrees Fahrenheit (minus 218.79 degrees Celsius)
- Boiling Point: minus 297.31 degrees F (minus 182.95 degrees C)
- Number of isotopes (atoms of the same element with a different number of neutrons): 11; three stable
- Most common isotopes: O-16 (99.757 percent natural abundance)
Priestly published his findings in 1774, beating out Swiss scientist Carl Wilhelm Steele, who had actually isolated oxygen in 1771 and written about it, but not published the work. Oxygen's third discoverer was Antoine-Laurent de Lavoisier, a French chemist who gave the element its name. The word comes from the Greek "oxy" and "genes," meaning "acid-forming."
Oxygen has eight total electrons — two orbit the nucleus in the atom's inner shell and six orbit in the outermost shell. The outermost shell can hold a total of eight electrons, which explains oxygen's tendency to react with other elements: Its outer shell is incomplete, and electrons are thus free for the taking (and giving).
Liquid and solid oxygen are pale blue.
Oxygen is paramagnetic.
Approximately 2/3 of the mass of the human body is oxygen.
Excited oxygen is responsible for the bright red and yellow-green colors of the aurora.