Group 7 - Halogens

• • Group 7 all have seven electrons in their outer shell and are non-metal elements and are toxic.
• • Fluorine - yellow gas at room temperature.
  • Chlorine - yellow-green gas.
  • Bromine - red-orange liquid.
  • Iodine - grey solid.
• • Non-metallic properties - poor conductors, low melting / boiling points, low density.
  • Diatomic molecules - F2, Cl2, Br2
• Trend in reactivity - Group 7

  As you go down:

  • Elements get less reactive.
  • Atomic number increases.
  • Number of shells increases.
  • Melting / boiling points increase.
• Why does reactivity decrease down Group 7?

  When Group 7 elements react, atom wants to fill outer shell and gains one electron. As you descend, distance between the nucleus and outer shell increases , meaning weaker attraction force so harder to gain an electron (less pull from positive nucleus), less reactive.