group 7 - halogens

• As you go down the group:

  • melting points
  • boiling points

  INCREASE!
• Halogens exist as diatomic molecules, they share 1 pair of electrons in a covalent bond, allowing both atoms a full outer shell
• At room temperature Chlorine (Cl₂) is a yellow-green gas
• At room temperature, Bromine (Br₂) is a red brown liquid
• At room temperature, Iodine (I₂) is a dark grey crystalline solid
• Halogens higher up in group 7 are most reactive because they can attract the outer electron of a metal more easily due to them being higher in reactivity
• When damp litmus paper is put into chlorine gas the litmus paper is bleached and turns white
• Halogens can react with Metals and Hydrogen to form Metal Halides and Hydrogen Halides
• Metal Halide

  Sodium + Chlorine -> Sodium Chloride

  2Na + Cl₂ -> 2NaCl

  
  

  Metals lose electrons and form positive ions
• Hydrogen Halide

  Hydrogen + Chlorine -> Hydrogen Chloride

  H₂ + Cl₂ -> 2HCl

  
  

  Metals lose electrons and form positive ions
• Displacement

  A more reactive Halogen will displace a less reactive one
• Chlorine will displace bromine because its more reactive

  Chlorine + Potassium bromide -> Potassium Chloride + Bromine