Chem yr 9

• Isotopes are atoms with the same amount of protons but different amounts of neutrons.
• Atoms can gain or lose electrons to form ions.
• Solid 


  Particles don’t move only vibrate

  least amount of energy

  lots of forces between particles

  particles are very compact

  regulars arrangement (fixed)

  gravity holds it down
• liquid


  take the shape of its container

  particles have energy

  random arrangement

  move freely but touching

  gravity holds it down
• gas


  low number of forces between particles

  random arrangement

  particles bounce around

  has the most energy

  less compact and has space
• diffusion is


  a movement of particles from an area of high concentration to an area of low concentration
• kinetic theory


  the idea that all partIckes are constantly moving
• diffusion only happens in


  gases and liquid
• why does diffusion only happen in gas/liquid

  because the particles can move and change position
• proton number = electron number
• electron shells

  1st shell = 2 electrons

  2nd shell = 8 electrons

  3rd shell= 8 electrons

  4th shell = 18 electrons
• periods = … groups = …


  no. of shells , no. of outer electrons
• the total mass of a product formed in a reaction is equal to the total mass of the reactants
• diatomic 


  exists in pairs
• solid to liquid


  melting
• liquid to gas


  evaporation
• gas to liquid


  condensation
• liquid to solid 


  freezing
• solid to gas


  sublimtion
• gas to solid 


  deposition
• An ionic compound is a giant structure of ions. ionic compounds are held together by strong electrostatic forces of attraction between oppositely charged ions. These forces act in all directions in the lattice which is called ionic bonding.
• properties of ionic substances 


  high melting point + b.pt

  good electrical conductivity

  soluble in water
• a covalent bond happens. when two atoms share a pair of electrons (usually where each atom donates 1 electron to share)
• there are simple and giant covalent bonds
• simple molecular substances 


  -small molecules

  • have weak intermolecular forces
  • small amount of energy needed to break
  • low m.pt/b.pt
• diamond


  high m.pt/b.pt

  very hard

  used for cutting and jewellery

  dones not conduct electricity

  needs lots of energy to break
• graphite 


  layers of hexagonal

  weak intermolecular forces

  can be used as a lubricant

  can conduct electricity
• molecule


  two or more atoms held together by covalent bonds
• covalent simple


  low m.pt / b.pt

  weak intermolecular forces

  shares electrons

  does not conduct electricity

  non-metals + non-metals
• covalent giant


  high m.pt/b.pt

  e.g. diamond, graphite, silicon oxide

  macromolecular

  non-metals + non-metals
• ionic


  high m.pt/b.pt

  conducts electricity when molten or dissolved in water

  transfer electrons

  soluble in water

  electrostatic forces

  metals + non-metals
• metallic


  mostly high m.pt/b.pt

  sea of delocalised electrons

  good conductors of heat

  giant lattice structure

  malleable + ductile

  electrostatic attraction between positive metal ions and delocalised electrons

  metal + metal
• alloys


  a mixture of two or more metals
• intermolecular forces


  weak forces found between small molecules
• intramolecular bonds


  strong covalent bond found within small molecules
• bonding in pure metals is regular arranged and bonding in alloys disrupts the regular arrangement which stops them from sliding over each other making bonding in alloys stronger
• valency 


  number of outer shell electrons
• Ar


  relative atomic mass
• relative atomic mass


  is how heavy atoms of that element are compared with the mass of an atom of carbon-12
• Mr


  relative formula mass