OXYGEN SYMBOL:฀O฀ PERIOD:฀2฀ GROUP:฀16฀(VIA)฀ ATOMIC฀NO:฀8

OXYGEN SYMBOL:฀O฀ PERIOD:฀2฀ GROUP:฀16฀(VIA)฀ ATOMIC฀NO:฀8

ATOMIC฀MASS:฀15.9994฀amu฀ VALENCE:฀2฀ OXIDATION฀STATE:฀–2฀ NATURAL฀STATE:฀

Gas ORIGIN฀OF฀NAME:฀From฀the฀Greek฀words฀oxys฀(which฀means฀sharp฀or฀acid)฀and฀gen฀

(which฀means฀forming);฀together฀they฀stand฀for฀“acid-forming.”฀In฀the฀eighteenth฀century,฀ it฀was฀believed฀that฀all฀acids฀contained฀oxygen.

ISOTOPES:฀There฀are฀a฀total฀of฀15฀isotopes฀of฀oxygen,฀three฀of฀which฀are฀stable.฀The฀stable฀ ones฀are฀O-16,฀which฀accounts฀for฀99.762%฀of฀all฀the฀oxygen฀on฀Earth;฀O-17,฀which฀ contributes฀only฀0.038%฀of฀the฀Earth’s฀oxygen;฀and฀O-18,฀which฀makes฀up฀just฀0.200%฀ of฀Earth’s฀oxygen.

Guide to the Elements |

ELECTRON฀CONFIGURATION ฀ Energy฀Levels/Shells/Electrons฀ Orbitals/Electrons

s2,฀p4

Properties There are three allotropes (different forms) of oxygen: (1) atomic oxygen (O), sometimes

referred to as nascent or “newborn” oxygen; (2) diatomic oxygen (O 2 ), or molecular oxygen (gas); and (3) ozone (O 3 ), also a gas. The atmospheric oxygen that we breathe is a very reactive nonmetal and is colorless, odor- less, and tasteless, but it is essential to all living organisms. It readily forms compounds with most other elements. With six electrons in its outer valence shell, it easily gains two more electrons to form a negative (–2) ion; or as covalent, it can share electrons with other elements to complete its outer shell.

Almost all the oxygen in the atmosphere (˜21%) is the allotropic form of molecular oxygen (O 2 ). This essential gas we breathe is the result of photosynthesis, which is how green plants (with chlorophyll) use the energy of the sun to convert carbon dioxide (CO 2 ) and water to starches and sugars with molecular oxygen as the by-product. Liquid oxygen has a slightly bluish cast to it. As it boils, pure oxygen gas is released. The melting point for oxygen is –218.79°C, its boiling point is –182.95°C, and its density is 0.001429 g/cm 3 .

Characteristics Oxygen is, without a doubt, the most essential element on Earth. It is required to support

all plant and animal life, and it forms more compounds with other elements than any other element.

Oxygen is soluble in both water and alcohol. Contrary to what many people believe, oxy- gen is NOT combustible (it will not burn), but rather it actively supports the combustion of many other substances. After all, if oxygen burned, every time a fire was lit, all the O 2 in the atmosphere would be consumed! Burning is a form of oxidation wherein oxygen chemically combines with a substance rapidly enough to produce adequate heat to cause fire and light, or to maintain a fire once started. The oxidation of iron is called rusting. Rusting in an example of “slow oxidation,” which is the reaction of O 2 with Fe to form Fe 2 O 3 or Fe 3 O 4 . This chemical reaction is so slow that the heat it produces is dissipated; thus, there is no fire. Recently a new allotrope of oxygen was discovered. When O 2 is subjected to great pressure, it is converted into O 4 , which is a deep red solid that is a much more powerful oxidizer than the other forms of oxygen.