Group 7 / Halogens

• Group 7 elements are also classed as..

  Halogens
• All halogens are

  • diatomic molecules
  • exist as pair of atoms
• Describe the trend of melting and boiling points in Halogens

  • increase
  • molecular mass increases
  • strength of intermolecular forces increase
  • a lot of energy is needed to overcome these forces
• Describe the reactivity in Halogens

  • decreases down the group
• States of halogens at room temp.

  1. Fluorine = Gas
  2. Chlorine = Gas
  3. Bromine = Liquid
  4. Iodine = Solid
  5. Astatine = Solid
• Why are halogens known as Group 7 elements?

  • have 7 electrons in the outer shell
  • share similar properties
• Colours of Halogens

  1. Fluorine = Pale-yellow
  2. Chlorine = Yellow-green
  3. Bromine = Red-brown
  4. Iodine = grey solid / purple vapour
• Explain reactivity of Halogens down the group

  1. Decreases
  2. Molecular mass increases down the group
  3. Outer electron becomes further away from nucleus
  4. Attraction weakens between outer electron and nucleus
  5. Harder to gain electron
• Displacement reactions occur...

  • when a halogen is more reactive than the ion of the other halogen

  potassium bromide + chlorine --> potassium chloride + bromine
• What if the displacing halogen is not more reactive than the halide ion?

  • a reaction does not occur
• What do the halogens gain?

  • 1 electron
  • stable electronic structure of a noble gas
• Are Halogens metals or non-metals?

  • non-metals
• Chlorine is flame..

  • flammable
  • handled in a fume cupboard