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Chemistry · Glossary

What is Halogens?

Also known as: halogen

Definition 28.7 University Chemistry — Year 1 · Chapter 28 — The p-Block II: Oxygen, Halogens and Noble Gases

The halogens are the elements of group 17 (F, Cl, Br, I, At), with seven valence electrons ns2^2np5^5. They exist as diatomic molecules XX2\ce{X2} and form halide ions XX−\ce{X-}.

Chlorine, a pale yellow-green gas (W. Oelen, CC BY-SA 3.0); bromine, a dark red liquid with an orange vapour (Jurii, CC BY 3.0); iodine, grey-black crystals with a metallic lustre (Dnn87, CC BY 3.0). Chlorine and bromine are sealed in glass ampoules. All Wikimedia Commons. Chlorine, a pale yellow-green gas (W. Oelen, CC BY-SA 3.0); bromine, a dark red liquid with an orange vapour (Jurii, CC BY 3.0); iodine, grey-black crystals with a metallic lustre (Dnn87, CC BY 3.0). Chlorine and bromine are sealed in glass ampoules. All Wikimedia Commons. Chlorine, a pale yellow-green gas (W. Oelen, CC BY-SA 3.0); bromine, a dark red liquid with an orange vapour (Jurii, CC BY 3.0); iodine, grey-black crystals with a metallic lustre (Dnn87, CC BY 3.0). Chlorine and bromine are sealed in glass ampoules. All Wikimedia Commons.
Chlorine, a pale yellow-green gas (W. Oelen, CC BY-SA 3.0); bromine, a dark red liquid with an orange vapour (Jurii, CC BY 3.0); iodine, grey-black crystals with a metallic lustre (Dnn87, CC BY 3.0). Chlorine and bromine are sealed in glass ampoules. All Wikimedia Commons.
Standard potentials of the halogen–halide couples at 25\, C, computed from tabulated Gibbs energies: the oxidising power falls steadily down the group.
Standard potentials of the halogen–halide couples at 25 ∘C25\,{}^{\circ}\mathrm{C}, computed from tabulated Gibbs energies: the oxidising power falls steadily down the group.
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