Group 7 (halogens)

• Halogens

  • 7 electrons in outer shell
  • Non metals
  • Exist as molecules made of pair of atoms which are covalent bonded toghether Cl2
• Halogens at top are gases at room tempature and at bottom are solids. What increases down the group

  Melting and boiling points and relative atomic mass
• Why are they a solid down the group at room tempature?

  Larger atoms have strong intermolecular forces so need alot of energy to overcome these bonds
• At room tempature what is chlorine?


  Pale green gas
• What is bromine at room tempature?


  Red-brown liquid
• What is iodine at room tempature?

  Dark grey solid
• Chlorine test

  • Place damp litmus paper in test tube of gas
  • Becomes bleached white
• Why does reactivity decrease down?

  Halogens react by gaining 1 electron to fill there outer shells.Number of electeon shells increase in each atoms and outer shell gets further from positive nuclues and becomes harder to gain extra electron
• When halogens react with other non metals whats it called?

  Molecular compounds
• Halogens react with hydrogen to form hydrogen halides

  • Hydrogen + chlorine -> hydrogen chloride
• How do hydrogen halides which are gases at room tempature becomes acidic solutions?

  They dissolve in water
• What are the ionic compounds between metal and halogen

  Metal halides
• Why do metal react with halogens

  Gain an electron from a metal atom to complete their outer shell
• The ionic bond holds negative halogens ion and positive metal ion
• A more reactive halogen can displace a less reactive halogen from it's aqueous solution of its salt
• Chlorine + pottasium iodide -> pottasium chloride + iodine
• A more reactive halogen will always oxidise a less reactive halide ion
• Group 7 + hydrogen -hydrogen halide
• what reaction can help to place elements

  in order of reactivity?

  displacement reaction