Ion

Ion
An ion is an atom, or group of atoms that has acquired a net electric charge as a result of gaining or losing one or more electron. There are two types of ions, a Cation and an Anion. Ions can also be in the form of Polyatomic ions.

An ion is an __ [|atom] __ or __ [|molecule] __ which has gained or lost one or more of its __ [|valence electrons] __, giving it a net positive or negative electrical charge.

History and discovery
The word //ion// is the Greek //ιον// (going), the present participle of //ιεναι//, //ienai//, "to go". This term was introduced by English physicist and chemist Michael Faraday in 1834 for the then-unknown species that //goes// from one electrode to the other through an aqueous medium.Faraday did not know the nature of these species, but he knew that since metals dissolved into and entered solution at one electrode, and new metal came forth from solution at the other electrode, that some kind of substance moved through the solution in a current, conveying matter from one place to the other.

Faraday also introduced the words **anion** for a negatively charged ion, and **cation** for a positively charged one. In Faraday's nomenclature, cations were named because they were attracted to the cathode in a galvanic device and anions were named due to their attraction to the anode.

Characteristics
Ions in their gas-like state are highly reactive, and do not occur in large amounts on Earth, except in flames, lightning, electrical sparks, and other plasmas. These gas-like ions rapidly interact with ions of opposite charge to give neutral molecules or ionic salts. Ions are also produced in the liquid or solid state when salts interact with solvents (for example, water) to produce "solvated ions," which are more stable, for reasons involving a combination of energy and entropy changes as the ions move away from each other to interact with the liquid. These stabilized species are more commonly found in the environment at low temperatures. A common example is the ions present in seawater, which are derived from the dissolved salts. All ions are charged, which means that like all charged objects they are: Electrons, due to their smaller mass and thus larger space-filling properties as matter waves, determine the size of atoms and molecules that possess any electrons at all. Thus, anions (negatively charged ions) are larger than the parent molecule or atom, as the excess electron(s) repel each other, and add to the physical size of the ion, because its size is determined by its electron cloud. As such, in general, cations are smaller than the corresponding parent atom or molecule due to the smaller size of its electron cloud. One particular cation (that of hydrogen) contains no electrons, and thus is //very much smaller// than the parent hydrogen atom.
 * attracted to opposite electric charges (positive to negative, and vice versa),
 * repelled by like charges
 * when moving, travel in trajectories that are deflected by a magnetic field.

Common Polyatomic Ions: 

Polyatomic Ion Charge = -1
 acetate - C 2 H 3 O 2 - bicarbonate (or hydrogen carbonate) - HCO 3 - bisulfate (or hydrogen sulfate) - HSO 4 - chlorate - ClO 3 - chlorite - ClO 2 - cyanate - OCN - cyanide - CN - dihydrogen phosphate - H 2 PO 4 - hydroxide - OH - nitrate - NO 3 - nitrite - NO 2 - perchlorate - ClO 4 - permanganate - MnO 4 - thiocyanate - SCN -

Polyatomic Ion Charge = -2
 carbonate - CO 3 2- chromate - CrO 4 2- dichromate - Cr 2 O 7 2- hydrogen phosphate - HPO 4 2- peroxide - O 2 2- sulfate - SO 4 2- sulfite - SO 3 2- thiosulfate - S 2 O 32-

Polyatomic Ion Charge = -3
  borate - BO 3 3- phosphate - PO 43   