the halogens

• halogens are non-metals. They exist as separate diatomic molecules and they all have the electron configuration of ns2p5
• fluorine at room temperature: yellow and gaseous
• chlorine at room temperature: green and gaseous
• bromine at room temperature: red/brown and liquid
• iodine at room temperature: grey and solid
• as you go down G7: boiling point,

  • increases
  • bigger size of molecules
  • induced dipole-dipole interactions (London dispersion force) increase
  • more energy required to overcome the bonds
• as you go down G7: reactivity,

  • decreases
  • atomic radius increases
  • moe shielding
  • less nuclear attraction
  • more energy required to gain the electron
• as you go down G7: atomic/ionic radius,

  • increases
  • more protons = more electrons
  • more shielding
  • electrons are further from nucleus
  • ionic - ions are larger than atoms - the added electron repels the others so the radius gets larger
• as you go gown G7: electronegativity,

  • decreases
  • more protons so increased nuclear charge, so should attract electrons more, BUT:
  • increased shielding means: less attraction on electrons
  • increased atomic radius means: attraction decreases as distance increases
• as you go down G7: oxidising power,

  • decreases
  • halogens are oxidising agents
  • they need one electron to complete the octet
  • oxidising power gets weaker down G7
• increasing nuclear charge attract electrons but this is offset by increased shielding and increasing atomic radius
• reducing equation: H2SO4 (aq) + 2e- + 2H+ (aq) --> SO2 (s) + 2H2O (l)
• test for halides:

  add AgNO3 (silver nitrate)

  equation: Ag+ (aq) + X- (aq) --> AgX (s)
• silver halides and dilute NH3

  AgCl - dissolves

  AgBr - N/A

  AgI - N/A
• Silver halides and concentrated NH3

  AgCl - dissolved already

  AgBr - dissolves

  AgI - N/A