Atoms

• element


  substance with only one type of atom
• compound


  a substance with two or more types of atoms, chemically bonded
• mixture


  a substance containing two or more types of atoms, not chemically bonded together
• separating mixtures - techniques


  1. Filtration
  2. crystallisation
  3. distillation (simple)
  4. chromatography
• History of the atom


  Democritus - ancient Greek - indivisible - Atomos

  Dalton - 1800 - atoms = tiny, hard, spheres

  JJ Thompson - 1897 - Plum Pudding - ball of positive charge with tiny negative charges randomly embedded into it - Electrons discovered

  Rutherford - gold foil experiment (alpha particle)- positively charged nucleus

  Bohr - electrons orbited at fixed levels (shells)

  Rutherford - Protons

  Chadwick - neutrons has no charge but have the same mass as protons
• Structure of Atom

  A) electrons on shells

  B) nucleus - protons + neutrons

  
• Neutrons


  charge - 0

  mass - 1

  found - nucleus
• Protons 


  charge - +1

  mass - 1

  found - nucleus

  determine what type of element an atom is
• Electrons 


  charge - -1

  mass - 1/2000

  found - shells
• mass number 


  number of protons and electrons (big number)
• atomic number 


  number of protons (small number)
• number of electrons = number of protons
• number of neutrons = mass number - atomic number
• periodic table


  arranged in columns (how many electrons on outer shell) and rows (how many shells)
• metals 


  conduct electricity and heat

  have high melting points

  left hand side of the table

  metallic bonding - they're strong, malleable

  shiny
• non-metals


  insulators

  right hand corner

  dull looking

  brittle

  aren't always a solid at room temp

  low density
• transition metals


  typical metals - good conductors, dense, strong, shiny

  more then one ion

  often coloured

  good catalysts
• isotopes 


  same number of protons but different number of neutrons (carbon)
• Group 0


  noble gases

  have 8 electrons on outer shell (except for He which only has 2)

  very stable

  unreactive - full outer shells

  melting point and boiling point gradually increases in temperature as you go down

  monatomic (single atoms not bonded together)

  colourless + non-flamable
• Group 1


  Alkali metals

  silvery solids that have been stored in oil

  very reactive

  soft - low density

  Li, Na, K - less dense then water

  one electron on the outer shell

  form ionic compounds with non-metals

  as you go down - increases in reactivity, lower MP/BP, higher relative atomic mass
• Group 7 


  Halogens

  non - metals, coloured vapours

  they are in pairs - F2, Cl2, Br2, I2

  7 electrons on their outer shells

  Halide - halogen + metal

  as you go down - less reactive, higher MP/BP, higher relative atomic mass
• Fluorine 


  very reactive

  poisonous

  yellow gas
• Chlorine


  fairly reactive

  poisonous

  dense green gas
• Bromine


  dense

  poisonous

  red-brown volatile liquid (easily evaporates)
• Iodine


  dark grey crystalline or purple vapour
• Group 1 metals reacting with water 


  what you see - fizzing, flame (potassium = lilac) , floating,