group 7

• fluorine (F2) is a very pale yellow gas. it is highly reactive.
• Chlorine (Cl2) is a greenish, reactive gas, poisonous in high concentrations
• Bromine (Br2) is a red-brown liquid that gives off brown/orange poisonous fumes
• Iodine (I2) is a shiny grey solid which sublimes to purple gas
• Trend in melting point and boiling point

  Increase down the group As the molecules become larger they have more electrons and so have larger van der waals forces between the molecules. As the intermolecular forces get larger more energy has to be put into break the forces. This increases the melting and boiling point.
• trend in electronegativity:

  • decreases down group.
  • atomic radius increases down group due to more electron shells, the nucleus is therefore less able to attract a bonding pair of electrons
• A halogen that is a strong oxidising agent will displace a halogen that has a lower oxidising power from one of its compounds.
• The oxidising strength decreases down the group. Oxidising agents are electron acceptors.