Chemistry Unit 2

• when metals form ions

  they lose electrons from their outer shell (become +)
• when non-metals form ions

  they gain electrons in their outer shell (- charge)
• the number of electrons lost or gained

  is the same as the ion charge
• when a non-metal and a metal react together


  the metal loses electrons to gain a full outer shell and the non-metal gains these electrons, forming a negative ion
• a non-metal and metal are held together by

  strong electrostatic forces
• Na+ =


  Na+ = Na+ + e
• Mg2+ =


  Mg2+ = Mg2+ - 2e
• Se2- =


  Se2- + 2 e = Se2-
• Br- =


  Br- + e = Br-
• Dot and cross pros

  Helps us understand how ionic compounds are formed
• Dot and cross

  1. Dont show how ions are arranged
  2. Dont show ion size
  3. Dont show structure
• Ionic compound structure


  Giant ionic lattice. Ions form a closely packed regular lattice arrangement and have string electrostatic forces between oppositely charged ions
• Ionic Compounds Properties

  1. High melting points due to strong electrostatic forces between the bonds
  2. If the compound is a solid, it cannot conduct electricity
  3. If melted, it can conduct electricity as the ions are free to move and can carry electric charge
• Empirical formula

  • If a dot and cross, count number of atoms
  • If a 3d diagram, first find the elements in the compound, then their charges and lastly balance the charges so that the charge is 0.
• Covalent bonds


  Non-metal atoms sharing electrons as the positively charged nuclei is strongly attracted to the negative charge of the electrons, pulling the bonds together and making the bonds strong
• Dot and cross diagram advantages


  - Useful for showing which atoms in the bonds come from
• Dot and cross diagram disadvantages

  • Doesnt show ion size
  • Doesnt show how atoms are arranged
• Displayed formula pros

  • Good way of showing how atoms are arranged
• Displayed formula CONS

  • Dont show where the atoms come from
  • Not a 3D diagram
• Nanoparticles


  Particles with a diameter between 1 nm and 100 nm
• Uses of nanoparticles


  • Help make new catalysts due to high surface area to volume ratio
  • Used in nanomedicine to deliver drugs directly to cells
  • Used in tiny electric circuits for computer chips due to ability to conduct electricity
  • Silver nanoparticles have antibacterial properties and used in surgical masks, wound dressings, and deodorants
  • Used in cosmetics to improve moisturisers
• Finding new ways to use nanoparticles is an important area of scientific research
• Nanoparticles have a large surface area to volume ratio


  This can cause the properties of a material to be different depending on whether it's a nanoparticle or in bulk
• The smaller the particle, the larger the surface area to volume ratio
• Nanoparticles are between ten and one hundred times larger than atoms and molecules
• State symbols


  (s) - solid, (l) - liquid, (g) - gas, (aq) - aqueous
• Physical changes are reversible
• In solids, there are strong forces of attraction between particles which hold them close together in fixed positions
• In liquids, there are weak forces of attraction between the particles which are randomly arranged and free to move past each other
• In gases, the force of attraction between the particles is very weak and they are free to move randomly
• Metallic bonding involves delocalised electrons that are free to move around and are shared between the positive metal ions
• The delocalised electrons in metallic bonding produce the properties of metals
• Most metals are solid at room temperature due to the strong metallic bonds
• Metals are good conductors of electricity and heat due to the delocalised electrons
• Metals are malleable as the layers of atoms can slide over each other
• Alloys are harder than pure metals because the different sized atoms disrupt the layers of metal atoms, making it more difficult for them to slide over each other
• Allotropes


  Diverse structural forms of the same element in the same physical state
• Allotropes of carbon


  • Diamond
  • Graphite
  • Graphene
  • Fullerenes
• Fullerenes


  • Molecules of carbon, shaped like closed tubes or hollow balls
  • Mainly made up of carbon atoms arranged in hexagons, but can also contain pentagons or heptagons
  • Buckminsterfullerene was the first fullerene discovered, with molecular formula C60 and a hollow sphere containing 20 hexagons and 12 pentagons
• Uses of fullerenes


  • Delivering drugs into the body
  • Industrial catalysts
  • Lubricants