Bonding

• Covalent Bonding


  When two or more non metal elements make a bond by sharing electrons to complete their outer shells
• Covalent Bonding


  Atoms share one or more pairs of electrons to get full shell structure
• Ionic Bonding

  When a metal atom reacts with a non metal atom, electrons in the outer shell of the metal atom are transferred. Metal atoms lose electrons to become positively charged ions. Non-metal atoms gain electrons to become negatively charged ions.
• The ions produced by metals in Groups 1 and 2 will give +1 and +2 charges and by non metals in Groups 6 and 7, -1 and -2 charges.
• Metallic Bonding

  The electrons in the outer shell of metal atoms are delocalised and so are free to move through the whole structure. The sharing of delocalised electrons gives rise to strong metallic bonds.
• There are no negative ions in a metallic bond, instead attraction is between positive metal ions and negative electrons
• Metals exist in lattices (big 3d structures). Unlike ionic lattices, metal lattices don't alternate between positive and negative
• Nanoparticles

  Particles that are between 1 and 100 nm in size (0.000000001 to 0.0000001 metres)
• Nanoparticles can also be defined as particles or molecules containing at a few hundred or so atoms
• Nanometre (nm)

  1 nm is equal to 1 billionth of a metre
• Categories of small particles

  • Coarse particles (2,500 to 1 million nm)
  • Fine particles (100 to 2,500 nm)
  • Nanoparticles (1 to 100 nm)
• Nanoparticles

  • As the side of a cube decreases in length by a factor of 10, its surface area to volume ratio increases by a factor of 10. This means nanoparticles have a very high surface to volume ratio, with the majority of atoms contained at the surface.
• Nanoparticles of a substance have different chemical and physical properties to that of the substances in bulk
• Uses of Nanoparticles

  • They make good catalysts due to high surface area to volume ratio
  • They have antibacterial properties and can be used in medical applications
  • They can conduct electricity and be used in miniaturized computing
• The effects of nanoparticles on human health are not yet fully understood, so they must be thoroughly tested before wider use