C1.2.6 - Group 7s (Halogens)

• Chemical properties and structure of group 7s

  Atoms of group 7 elements all have seven electrons in their outer shell. This means that the halogens all have similar chemical reactions.

  When a group 7 element takes part in a reaction, its atoms each gain one electron. These atoms form negatively charged ions. The ions have a stable arrangement of electrons, with a complete outer shell.
• What type of elements are halogens?

  The halogen elements are the six elements in Group 7 of the periodic table. Group 7 occupies the second column from the right in the periodic table and contains fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At), and tennessine (Ts). Astatine and tennessine are radioactive elements with very short half-lives and thus do not occur naturally. They are non-metals.
• Reactions with metals in group 7

  The halogens react with metals to produce salts called metal halides (the word 'halogen' means 'salt former'). For example, chlorine reacts with sodium:

  Sodium + chlorine → sodium chloride

  2Na(s) + Cl2(g) → 2NaCl(s)

  Sodium and chlorine react vigorously when heated, giving an orange flame and clouds of white sodium chloride.

  The halogens become less reactive going down group 7.
• Reactions with non-metals in group 7

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

  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.
• Displacement reaction of halogens

  In a displacement reaction, the more reactive halogen atoms oxidise the less reactive halide ions, causing the halide ions to lose electrons and form halogen atoms. The halogen atoms then gain electrons to form halide ions, which are reduced.
• Solutions of salts of halogens

  Halogens react to a small extent with water, forming acidic solutions with bleaching properties. They also undergo redox reactions with metal halides in solution, displacing less reactive halogens from their compounds.