Ion: what is it, types and examples

What is an ion?

An ion is a molecule or atom that has a positive or negative electric charge. That is, an ion is an atom whose electric charge is not neutral.

The word ion comes from the Greek ἰών , which means 'going'. This word was first used in the English language in 1834 thanks to the scientist Michael Faraday, who in 1830 had proposed the existence of ions. Then, in 1884, the scientist Arrhenius developed the theory that led to its verification.

Ions are formed by ionization. The term refers to the phenomenon of electron gain or loss of the atom when it is subjected to certain processes. The loss or gain of electrons allows the atom to acquire an electrical charge, transforming itself into an ion. If the electric charge is positive, it is called a cation; if it is negative, it is called an anion. It is concluded that the non-ionized atoms are electrically neutral.

The following form is used to represent the ions:

• The symbol of the atom is written (for example, Al for aluminum); The plus (+) or minus (-) symbol is added to indicate if the charge is negative or positive; If the number of electrons gained or lost is greater than 1, the quantity is indicated.

For example,

• A simple hydrogen cation is represented like this: H ⁺ A simple aluminum cation is represented like this: Al ^{3 +}

Ions can be monoatomic (formed by a single atom) or polyatomic (formed by two or more atoms).

For example,

• Monoatomic: Be ²⁺ (Beryllium); Cs ⁺ (Cesium); Li ⁺ (Lithium). Polyatomic: NH ₄ ⁺ (Ammonium); H ₃ O ⁺ (Hydronium or Oxonium); NO ₂ ⁺ (Nitronium).

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• What is ionization? Atom.

Ion types

There are two types of ions, defined according to the electrical charge they contain. Their names are cations and anions.

Anion

Anions are negatively charged ions. They are formed as a consequence of the electron gain. Therefore, anions are characterized by having more electrons than protons in their composition. The word anion means 'he who goes down.'

Examples of anions

• Arsenide As ^{3 -} Azide N ³⁻ Bromide Br ^- Carbide C ⁴⁻ Fluoride F ^- Phosphide P ³⁻ Oxide O ²⁻ Peroxide O ₂ ^{2 -} Sulfide S ²⁻

Cation

Cations are positively charged ions. They are formed as a consequence of the loss of electrons. This means that cations always have more protons than electrons. The word cation means 'he who goes up.'

Examples of cations

• Calcium Ca ^{2 +} Chromium (II) Cr ^{2 +} Copper (I) Cu ⁺ Iron (II) Fe ^{2 +} Mercury (II) Hg ^{2 +} Nickel (III) Ni ^{3 +} Silver Ag ⁺ Lead (IV) Pb ^{4 +} Potassium K ⁺ Sodium Na ⁺ Zinc Zn ^{2 +}