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).

Hydrogen (represented with a H) add Chlorine (represented with Cl) to make hydrochloric acid (HCl). The hydrogen shares an electron with the chlorine.

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.

Hydrogen represented as an "H" in a circle overlapping a circle with the letters "Cl" representing a chlorine atom. The hydrogen and Chlorine share 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.

A sodium atom gives an electron to a chlorine atom. The Sodium ion and Chlorine ion are shown with full outer shells below showing they've become stable.
  • 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