Halogens and Halides in industrial processes

• Halogens


  Group 17 elements on the periodic table, consisting of: fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At)

  
• Halogens


  • Toxic, non-metallic elements
  • Form diatomic molecules (X2) in their elemental states
  • Bonds in diatomic molecules are non-polar covalent single bonds
  • Readily combine with most elements and are never seen uncombined in nature
  • Fluorine is the most reactive halogen and astatine is the least reactive

  
• Halides


  • Binary compounds made up of any other element and a halogen
  • Halide ions are halogen atoms with a negative charge (F-, Cl-, Br-, I-, At-)

  
• Periodic trends in the halogens

  • Melting and boiling points increase down the group
  • Atomic radius increases down the group
  • Ionization energy decreases down the group
  • Electronegativity decreases down the group
  • Electron affinity decreases down the group
  • Reactivity of elements decreases down the group
• Reactions of halogens


  1. Displacement reactions

  2. Reaction with hydrogen

  3. Reaction with metals

  
• Displacement reactions


  • Cl2 + 2KBr → 2KCl + Br2
• Reaction with hydrogen


  • H2 + Cl2 → 2HCl
• Reaction with metals


  • 2Na + Cl2 → 2NaCl
• Industrial uses of halogens

  • Fluorine (F): Aluminum production, Dental care, Organic synthesis
  • Chlorine (Cl): Water treatment, PVC production, Organic chemistry
  • Bromine (Br): Flame retardants, Medicinal applications
  • Iodine (I): Medical applications, Nutrition, Photography
  • Astatine (At): No proven uses

  
• Astatine is radioactive and rare, so there are no proven uses for this halogen element

  
• Interhalogen compounds


  Molecules containing two or more different halogen atoms and no atoms of elements from any other group
• Interhalogen compounds


  • Chlorine monofluoride (ClF), Bromine monofluoride (BrF), Bromine monochloride (BrCl)
• Polyhalides


  Compounds containing more than one halogen atom
• Polyhalides


  • Potassium triiodide (KI3), Cesium pentabromide (CsBr5)
• Halogens and some of their compounds can be toxic or corrosive, and improper disposal or accidental release can lead to environmental pollution and health risks