The Periodic Table: Group 7

The Periodic Table: Group 7

Group 7: The Halogens

General Properties

• Elements found in Group 7 of the Periodic Table referred to as Halogens.
• Each Halogen atom has seven electrons in its outer shell, making them highly reactive.
• Exist mostly as diatomic (composed of two atoms) molecules and include elements like Fluorine, Chlorine, Bromine, Iodine and Astatine.
• Are poor conductors of heat and electricity as they are non-metals.

Reactivity

• Decreases down the group. The attraction between the nucleus and the outer shell decreases as the atomic size increases, making it harder to gain additional electrons.
• Halogens react by gaining an electron to form a negative ion.
• Tend to react readily with Alkali Metals (Group 1) and Alkaline Earth Metals (Group 2) to create salts.

Physical Properties

• Become darker in colour and higher in mass as you go down the group.
• At room temperature, Fluorine and Chlorine are gases, Bromine is a liquid, and Iodine and Astatine are solids.
• Boiling and melting points increase down the group due to increase in dispersive forces.

Chemical Properties

• Highly electronegative; they have the ability to attract and capture electrons.
• Can act as strong oxidising agents, making them beneficial in many chemical reactions.
• Form -1 ions when reacting with metals.

Examples of Reactions

• Reaction of Sodium with Chlorine: 2Na(s) + Cl2(g) -> 2NaCl(s)
• Reaction of Fluorine with Hydrogen: H2(g) + F2(g) -> 2HF(g)

Uses of Halogens

• Chlorine is used for disinfection of water and in the production of plastics.
• Fluorine is used in fluoride toothpaste to prevent tooth decay.
• Iodine is used as an antiseptic for treating small cuts and wounds.