Reactions of Halogens

Reactions With Non-Metals

Halogens react with other non-metals to form covalent compounds. For example, hydrogen reacts with chlorine to form hydrochloric acid (HCl).

A chemical diagram showing the formation of a hydrogen chloride molecule. Initially, separate hydrogen and chlorine atoms are depicted with their respective electrons. As they combine, there's an indication of a bonding electron pair forming the H-Cl bond. The chlorine atom retains a lone electron pair after the bond is formed, resulting in the H-Cl molecule.

In this reaction, the hydrogen atom shares electrons with the chlorine atom, forming a covalent bond between them. Hydrogen requires only one electron to complete its outer shell, while chlorine requires one electron as well. By sharing electrons, both atoms can complete their outer shells and form a stable compound.

A graphical representation of a hydrogen atom and a chlorine atom with overlapped electron clouds, illustrating the sharing of electrons between them. The caption reads "Hydrogen and chlorine sharing electrons".

  • Covalent bonds form between non-metals, whereas ionic bonds form between a metal and a non-metal.

Reactions with Metals

Halogens react with metals to form ionic compounds, known as metal halide salts. For example, sodium reacts with chlorine to form sodium chloride (NaCl), otherwise known as table salt.

Diagram illustrating the ionic bond formation between a sodium atom and a chlorine atom. The top half shows individual sodium and chlorine atoms with their electron configurations. A directional arrow indicates the transfer of an electron from sodium to chlorine. The bottom half depicts the resultant sodium and chlorine ions with their respective positive and negative charges, connected by a dotted line representing the ionic bond to form sodium chloride (NaCl).
  • Sodium (Na) has 1 electron in its outer shell, so it needs to lose that electron to have a full outer shell.
  • Chlorine (Cl) has seven electrons in its outer shell, so it needs to gain one electron to complete its outer shell.

As a result, the sodium atom loses its outer electron to chlorine, resulting in both atoms having a complete outer shell.

However, this transfer of electrons results in sodium now having 11 protons and 10 electrons. Because protons have a positive charge and electrons have a negative charge, sodium becomes a positive ion (Na+) with a +1 charge. Meanwhile, chlorine now has 17 protons and 18 electrons and becomes a negative ion (Cl) with a -1 charge.

So, when reacting with metals, halogens gain an electron to complete their outer shell and form a negative ion, while metals lose an electron to become a positive ion. The positive and negative ions then attract each other and form an ionic bond, resulting in the formation of an ionic compound.


Halogen ions are called halides, and they form when halogens react with metals. The table below shows the halides that form from different halogens.

HalogenHalide Formed

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