What is an ion?

We explain what an ion is and how these molecules can be constituted. Also, examples of ions and what an anion is.

  1. What is an ion?

In chemistry,  an electrically charged molecule and constituted by an atom or molecule that is not electrically neutral is known as an  ion , that is, in its constitution it has gained or lost electrons (ionization).

The ions  can consist of two or more atoms (polyatomic) of different nature, or of a single atom (monoatomic). In any of the cases, we will talk about a  cation  (or cations) when it is a positively charged ion (that is: lack of electrons), and we will talk about an  anion  (or anions) when it is a negatively charged ion (it is say: with excess electrons).

Other types of ions are also known, based on their electrical charge, known as  dianions  (when they have both electric charges), zwitterions (which has a neutralized double charge to reach the neutral), or ionic radicals (free ions of enormous reactivity and instability ). In general, ions are very reactive and tend to be joined by electromagnetism with other molecules.

The ions  play an indispensable role in life, especially those of calcium, potassium and sodium , whose importance in the transit of cell membranes  and neurotransmitters has been studied extensively. For the rest, the understanding of ions  has allowed us to develop plasma technology and even measure water quality based on the ionic salts dissolved in it.

  1. Ion examples

Azide is a simple anion.

The best known ions are:

Cations simple . Composed of a single atom with positive charge:

  • Aluminum (Al3 +)
  • Cesium (Cs +)
  • Chromium III or chromic ion (Cr3 +)
  • Chrome VI or perchromic ion (Cr6 +)
  • Hydrogen or proton (H +)
  • Helium or alpha particle (He2 +)
  • Lithium (Li +)
  • Iron II or ferrous ion (Fe2 +)
  • Iron III or ferric ion (Fe3 +)
  • Nickel III or nickel ion (Ni3 +)
  • Tin II or stannous ion (Sn2 +)
  • Tin III or static ion (Sn3 +)

Polyatomic cations  . Composed of two or more atoms with positive charge:

  • Ammonium (NH4 +)
  • Oxonium (H3O +)
  • Nitronium (NO2 +)
  • Mercury I or mercury ion (Hg22 +)

Simple anions . Composed of a single atom with negative charge:

  • Azide (N3-)
  • Bromide (Br-)
  • Carbide (C4-)
  • Chloride (Cl-)
  • Fluroride (F-)
  • Phosphide (P3-)
  • Nitride (N3-)
  • Sulfide (S2-)

Oxyanions . Composed of oxygen and other elements, they have a negative charge:

  • Arsenate (AsO43-)
  • Borate (BO33-)
  • Hypobromite (BrO-)
  • Bicarbonate (HCO3-)
  • Chlorate (ClO3-)
  • Chlorite (ClO2-)
  • Hypochlorite (ClO-)
  • Dichromate (Cr2O72-)
  • Hydrogen sulfate or bisulfate (HSO4-)
  • Hydrogen sulphite or bisulfite (HSO3-)
  • Silicate (SiO44-)

Anions of organic acids . Coming from organic molecules, they have a negative charge: 

  • Acetate (C2H3O2-)
  • Oxalate (C2O42-)
  • Bioxalate (HC2O4-)

Other anions . With negative charge and more than one atom:

  • Bisulfide (HS-)
  • Amide (NH2-)
  • Cyanato (OCN-)
  • Thiocyanate (SCN-)
  • Cyanide (CN-)
  • Hydroxide (HO-)
  1. Anion

Sulfite is a polyatomic anion.

Anion (or anions) is known as ions that have a negative electrical charge , that is, have gained electrons in a chemical reaction that gave rise to them. They may consist of one or several atoms, but in even the latter case the overall charge of the molecule (its oxidation state ) is always negative.

There are three types of anions:

  • Monatomic . Those constituted by a single atom that has gained electrons. For example: Chloride (Cl-).
  • Polyatomic . They come from a molecule that has gained electrons in a chemical reaction, or from an acid that has lost protons. For example: Sulfite (SO32-).
  • Acids . They come from a polyrotic acid (which have multiple ionizable hydrogens) to which protons have been extracted. For example: Diacid phosphate (H2PO4-).

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