When an atom or molecule loses its electrical neutrality happens to receive the denomination of ion. The process associated with the gain or loss of one or more electrons that characterizes the atomic structure of a neutral atom or compound is called ionization. The most basic knowledge of ion formation is attributed to the English chemist Humphrey Davy (1778-1829) and his disciple, Michel Faraday (1791-1867). For instance: chloride anions, calcium cation, sulfide anion.
When a electrically neutral atom gains one or more electrons, an anion is formed. Anions are attracted to the anode, which is an electrode in which a substance loses electrons, that is, it oxidizes, and this occurs through an oxidation reaction.
On the other hand, when an electrically neutral atom loses one or more electrons, a cation. The cations are attracted to the cathode, which is an electrode in which a substance gains electrons, that is, it is reduced, and this occurs through a reduction reaction. The electrons that are lost are those of the last energy level of the neutral atom.
In the anionsEach electron in the atom, which is originally neutral, is strongly held by the positive charge of the nucleus. However, unlike the rest of the other electrons in the atom, in anions the additional electron is not linked to the nucleus by Coulomb forces, (electrical interaction forces of two point charges that are at rest and are directly proportional to the multiplication of the magnitude of the two charges and inversely proportional to the square of the distance that separates both charges).
Thus, in anions, the additional electron is bound by the polarization of the neutral atom. Due to the addition of electrons, the anions are larger than the corresponding neutral atom, while the size of the cations is smaller than that of the corresponding neutral atoms, due to the loss of electrons.
At room temperature, many sign ions opposite they bind strongly to each other following a regular and orderly scheme that gives rise to the formation of crystals, like table salt (sodium chloride). Often times, when salts are dissolved in a solvent, they ionize easily.
Being dissolved, ions are the basis of important industrial processes such as electrolysis and give foundation to essential devices of the modern world such as batteries and accumulators. Different ions participate in the enzymatic oxidation and reduction processes, so characteristic of countless biochemical reactions that occur in living beings.
The elements that normally have the greatest facility to ionize positively (to lose electrons and thus generate cations) are metals. Certain nonmetals generally form anions and noble gases such as helium or argon do not form ions.
In general, ions are chemically more reactive than neutral atoms and molecules and can be monatomic or polyatomic, inorganic or organic.
Examples of ions
Listed below are 20 examples of ions, including anions, cations, monatomic and polyatomic ions.
- Chloride anions (Cl–)
- Sulfate anions (SO42-)
- Nitrate anions (NO3–)
- Calcium cation (Ca2+)
- Manganese (II) cation (Mn2+)
- Hypochlorite anion (ClO–)
- Ammonium cation (NH4+)
- Ferric cation (Fe3+)
- Ferrous cation (Fe2+)
- Magnesium cation (Mg2+)
- Silicate anions ( [SiO4]4- )
- Borate anions ( [BO3]3- )
- Permanganate anion (MnO4–)
- Sulfide anion (S2-)
- Phosphate anion (PO43-)
- Metaphosphate anion (PO3–)
- Carbonate anions (CO32-)
- Citrate anion ( [C3H5O (COO)3]3- )
- Malate anion ([C4H4O5]2-)
- Acetate anion ( [C2H3O2]-)