Chemistry revision

• The radius of an atom is 0.1nm
• Most of the mass is not in the shell of the atom, but in the centre
• Atom components


  • Charge
  • Relative Mass
• Overall charge of an atom

  No charge
• Compound


  2 or more elements, chemically joined
• Compounds


  • salt water
  • magnesium oxide
  • sodium chloride

  
• The circled items are compounds because they have 2 or more elements chemically joined
• Mass number


  Total number of protons and neutrons
• Neutron number


  Atomic mass - proton number
• Isotopes


  Elements with different number of neutrons but same number of protons
• Balancing chemical equations


  1. Mg + O2 -> MgO

  2. Be + S -> BeS

  3. Be + F2 -> BeF2

  4. K + Cl2 -> 2KCl
• Mixture


  Two or more elements together, not chemically joined and can be easily separated
• Mixtures


  • Salt water
  • Sand and water
• Ratio of elements in compounds


  • MgCl2 = 1:2
  • K2O = 2:1
• Distillation


  Separation technique

  
• Fractional distillation


  Separation technique

  
• Chromatography


  Separation technique to separate inks in pens
• Collecting salt from rock salt

  1. Grind the mixture

  2. Add water and stir

  3. Filter the mixture

  4. Evaporate the salt water
• NaCl


  Sodium chloride, sodium and chlorine
• MgO


  Magnesium oxide, magnesium and oxygen

  
• MgS


  Magnesium sulfide, magnesium and sulfur

  
• FeS


  Iron sulfide, iron and sulfur
• Argon, neon, xenon, radon


  Noble gases
• Noble gases


  • Full outer shell of electrons
• The boiling points of the noble gases increase as you go down the group
• Reactivity of alkali metals

  Increases as you go down the group
• Sodium reacting with water


  sodium + water -> sodium hydroxide + hydrogen
• Halogens


  • chlorine
  • fluorine
  • iodine
  • astatine
• Balancing halogen reactions


  1. Br2 + 2KI -> 2KBr + I2

  2. Cl2 + 2NaI -> 2NaCl + I2

  3. F2 + KCl -> 2KF + Cl2
• Properties of metals and non-metals


  • Metals: strong, low density, malleable, good conductors

  Non-metals: dull, brittle, poor conductors
• James Chadwick discovered the neutron
• Word equations for reactions


  sodium + chlorine -> sodium chloride

  lithium + iodine -> lithium iodide

  potassium + bromine -> potassium bromide
• Groups in the periodic table are arranged according to their properties
• Niels Bohr discovered that electrons orbit the nucleus in shells

  
• Some of the gaps Mendeleev left have been filled as scientists have found the missing elements
• The radius of an atom is 0.1nm
• Most of the mass is in the centre of the atom, not the shell
• Overall charge of an atom

  No charge
• Compound


  2 or more elements, chemically joined
• Compounds


  • salt water
  • magnesium oxide
  • sodium chloride