The Halogens

• Group Seven Elements


  Molecules with two atoms
• Moving down Group Seven

  Melting and boiling points of the group seven elements increase
• Group Seven is also called the halogens
• All the elements in Group Seven are non-metals
• Group Seven elements


  Have seven electrons in their outer energy level
• Formation of Group Seven molecules

  1. Two atoms of a Group Seven element overlap their outer energy levels

  2. They share a pair of electrons

  3. This shared pair of electrons is called a covalent bond

  4. Every Group Seven element forms a molecule consisting of two atoms joined by a covalent bond
• The covalent bond can be represented as a stick between the two atoms
• Moving down Group Seven

  The relative molecular mass of the halogens increases
• Room temperature is around 20°C
• Physical state of halogens at room temperature

  • Fluorine and chlorine are gases
  • Bromine is a liquid
  • Iodine is a solid
• Fluorine - pale yellow gas
• chlorine - pale green gas
• bromine - volatile red-brown liquid
• Iodine - dull blue-black solid
• Astatine - dull grey-black radioactive solid
• Have - hydrogen

  No - Nitrogen

  Fear - Fluorine

  Of - Oxygen

  Cold - Chlorine

  Beer - Bromine
• Displacement - when a more reactive element takes place of a less reactive element
• Cyclohexane - chlorine (colourless), bromine (orange) and iodine (purple

  KCl - chlorine (no reaction), bromine (orange), iodine (purple)

  KBr - chlorine (orange), bromine (no reaction) iodine (purple)

  KI - chlorine (purple), bromine (purple), iodine (no reaction)