Chem

• Chlorine


  Group 7 element, a halogen
• Reaction of lithium and chlorine

  2Li + Cl2 → 2LiCl
• Halogens


  • Non-metals: fluorine, chlorine, bromine, iodine
  • Become less reactive going down the group
  • Harder to gain an extra electron as outer shell is further from nucleus
  • Melting and boiling points become higher going down the group
• Noble gases


  • Group 0 elements: helium, neon, argon
  • Unreactive as they have full outer shells
  • Colourless gases at room temperature
  • Boiling points increase going down the group due to greater intermolecular forces
• Electronic structure


  • Electrons found in shells
  • Maximum of 2 in innermost shell, then 8 in 2nd and 3rd shells
  • Inner shell filled first, then 2nd, then 3rd
• Atomic models


  • Dalton - atoms as solid spheres
  • Thomson - plum pudding model
  • Rutherford - mass concentrated in nucleus, most of atom is empty space
  • Bohr - electrons in shells orbiting nucleus
  • Chadwick - discovered neutrons in nucleus
• Products of crude oil distillation

  • Gas (20°C)
  • Gasoline (petrol) (150°C)
  • Kerosene (200°C)
  • Diesel oil (300°C)
  • Fuel oil (370°C)
  • Lubricating oil, paraffin wax, asphalt (400°C)
• Metals


  • Strong, malleable, good conductors of electricity and heat
  • Bond metallically
• Non-metals


  • Dull, brittle, not always solids at room temperature
  • Poor conductors of electricity and heat
• Transition metals


  • Block of elements between groups 2 and 3
  • Have metallic properties
  • Can form more than one ion
  • Ions are often coloured
  • Good catalysts
• Solid


  • Particles in a regular pattern
  • Particles vibrate in fixed positions
  • Particles tightly packed
  • Low kinetic energy
• Liquid


  • Particles randomly arranged
  • Particles able to move around each other
  • Greater kinetic energy than solids
  • Can flow and take shape of container
• Gas


  • Particles randomly arranged
  • Particles able to move quickly in all directions
  • Highest kinetic energy of the three states
  • Can flow and fill container
  • Can be compressed
• Limitations of the particle model: chemical bonds not represented, particles not always spherical, particles mostly empty space
• Identifying physical state


  • If temperature < melting point, solid
  • If temperature between melting and boiling point, liquid
  • If temperature > boiling point, gas
• State symbols


  Solid (s), liquid (l), gas (g), aqueous (aq)
• Formation of ions


  • Metals lose electrons to become positively charged
  • Non-metals gain electrons to become negatively charged
• Metallic bonding


  • Positive metal ions surrounded by sea of delocalised electrons
  • Strong electrostatic forces of attraction
• Ionic bonding


  • Occurs between metal and non-metal
  • Metals lose electrons, non-metals gain electrons
  • Opposite charges attract
• Ionic compounds


  • Form giant lattices
  • High melting and boiling points
  • Do not conduct electricity as solids, but can conduct when molten or in solution
• Covalent bonding


  • Sharing of electron pairs between non-metal atoms
  • Simple covalent structures have low melting and boiling points
  • Do not conduct electricity
• Dot and cross diagrams can show covalent bonding in simple molecules
• Diamond


  • Each carbon bonded to 4 others
  • Very strong covalent bonds
  • High melting and boiling point
  • Does not conduct electricity
• Graphite


  • Layers of carbon atoms in hexagons
  • Each carbon bonded to 3 others with 1 free electron
  • Layers held by weak intermolecular forces
  • High melting point, can conduct electricity
• Graphene


  • Single layer of graphite
  • Very strong covalent bonds
  • Can conduct electricity
  • Useful in electronics and composites
• Fullerenes and nanotubes


  • Molecules of carbon in hollow tubes or balls
  • Can be used to deliver drugs
• Nanoparticles


  • 1-100nm in size
  • High surface area to volume ratio
  • Possible health risks due to small size
• Polymers


  • Long chain molecules made of monomers
  • Atoms bonded by covalent bonds
  • Intermolecular forces between chains
• Relative formula mass (M ) is the sum of the relative atomic masses of the atoms in a compound
• Carbon nanotubes


  Tiny carbon cylinders that are very long compared to their width. Nanotubes can conduct electricity as well as strengthening materials without adding much weight
• Buckminsterfullerene


  Molecules of carbon that are shaped like hollow tubes or balls, arranged in hexagons of five or seven carbon atoms. They can be used to deliver drugs into the body
• Particle sizes


  • nanoparticle (1–100nm)
  • fine particles (PM₂₅) (100–2500nm)
  • coarse particles (PM1₀) (2500–10000nm)
• Relative atomic mass (A )


  An element's relative mass compared to the mass of an atom of carbon-12
• Relative formula mass (M )


  The sum of all the relative atomic masses (A ) of the atoms in the formula
• Calculating relative formula mass

  • Hydrochloric acid (HCl) = 1 + 35.5 = 36.5

  Sulfuric acid (H₂SO₄) = (1 × 2) + 32 + (16 × 4) = 98
• Neither A or M values have any units
• In a closed system


  The mass in a chemical reaction will remain constant
• In a non-enclosed system

  Changes in mass can occur, such as when a gas is released
• No atoms are created or destroyed in a chemical reaction, they are just rearranged
• Uncertainty


  A measure of the variability in scientific data