Trends down the halogens.

• Trend in melting and boiling point.

  Increase down the group;

  As the molecules become larger they have

  more electrons. - 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 points.
• Trend in electronegativity.

  As you go down the group the electronegativity of the elements decreases.

  Down the group the atomic radii increases due to the increasing number of shells. The nucleus is therefore less able to attract the bonding pair of electrons.
• Oxidising strength.

  Decreases down the group; its ability to accept an electron is less. Less likely to gain electrons from another substance in a chemical reaction; a worse oxidising agent.