Ion

A ion (of the Greek grc ἰόν, ion , “which goes”) is made up starting from a Atome or of a Molécule (group of atoms) which gained or lost one or more electron S (negative charges). The core of a monoatomic ion has the same number of protons (Z) and the same number of neutrons as the atom corresponding, but remotely by the number of electrons; this is why one notes it with the same symbol but supplemented by the load.

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This name was given towards 1830, by Michael Faraday, with the chemical species responsible for the electric conductivity of the liquids. It was necessary to await 1885 so that Swedish Svante August Arrhenius proposes an explanation of the mechanism of conduction, for which it will be rewarded by the Nobel Prize in 1903.

Beams of ions of high energy are used in atomic Physique, Nuclear physics and Physique of the particles (see Particle accelerator).

Ci below, we consider only the stationary ions or low speed.

A Anion consists of an atom (or grouping) having gained one or more electron (S); it has a negative electric charge because it then contains more electrons (−) that protons (+). For example, the ion chloride, noted Cl − , is the chlorine atom (Cl) having gained an electron.

An anion is a negative ion.

A Cation consists of an atom (or grouping) having lost one or more electron (S): it has a positive electric charge because it then contains less electrons (−) that protons (+). For example, the ion sodium, noted Na + , is the sodium atom (Na) having lost an electron.

A cation is a positive ion.

Any chemical compound being electrically neutral, if it contains ions, it then contains necessarily at the same time cations and anions. The matter being overall neutral, the load of the cations is compensated by those of the anions.

Ionic solids

These solids consist of an alternate stacking of cations and anions connected by connections known as “ionic”; the cohesion of the unit is ensured by the electrostatic forces. For example, the salt of table (Sodium chloride) is a stacking of ions chloride and ions sodium.

These solids are easily soluble in the Eau or other polar solvents, because the ions are there easily solvates (dispersed among the molecules of solvent).

Ionization of molecular compounds

In certain molecular bodies, certain atoms attract more the electrons of connections than others; it is said that the bonds between atoms are polarized. In contact with a polar solvent, like the Water, the molecules of these compounds the such sulphuric Acid , the Ammonia or the Carbon dioxide, dissociate in ions during dissolution.

Ionic solutions

A liquid containing of the ions among solvent is called ionic solution. In the solution, the ions move easily under the effect of an electric field, from where the strong electric conductibility of the ionic solutions. The measurement of the electric conductivity of a solution (Conductimetry) thus makes it possible to consider its content total of ions. An ionic solution is electrically neutral.

Thus, the water of the Océan S, which constitute the most important hydrous reserve of the Earth, is rich in ions:

Examples of ions

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Ionization of gases

The Ionization of gases can be realized thanks to:

  • a very high Temperature:

heat - typically more: 10000 K - brings energy necessary to this ionization and produces a plasma, Gaz partially or completely ionized. Constituted of a mixture of ions, charged positively, and electrons, negative, plasma is as a whole electrically neutral. The Sun is a plasma; radiative ionization occurs under the action of a radiation short wavelength, known as ionizing, the such Ultraviolet rays or the X-rays: the gases of high the atmosphere, the Ionosphere, ionized by the solar Radiation, take part in the formation of layers reflecting the waves radio on short waves;

  • a intense Electric field:

the gun plasma, still called ICP (Spectrométrie of emission with inductive coupling), is a technique which uses a plasma, generated thanks to an intense electric field, to vaporize and ionize the compounds to be analyzed. The flashes are another example of electric ionization;

  • a Beam of particles:

the collisions between the gas molecules of the ionosphere with the solar particles of high energy can generate polar lights.

Simple: Ion Zh-classical: 離子 Zh-yue: 離子

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