Chemistry paper 1

• Atom


  The smallest part of an element that can exist
• Atom


  • Have a radius of around 0.1 nanometres and have no charge
• Subatomic particles


  • Proton
  • Neutron
  • Electron
• Proton


  Positively charged particle
• Neutron


  Neutral particle
• Electron


  Negatively charged particle
• Mass number


  The sum of the protons and neutrons in the nucleus
• Atomic number


  The number of protons in the atom
• Rutherford's scattering experiment


  1. A beam of alpha particles were directed at very thin gold foil

  2. Most of the alpha particles passed right through

  3. A few positive alpha particles were deflected by the positive nucleus

  4. A tiny number of particles reflected back from the nucleus
• Rutherford's model of the atom

  • Positively charged nucleus at the centre surrounded by negative electrons
  • Electrons orbit the nucleus at specific distances
• Discovery of the electron

  1897
• Rutherford's scattering experiment


  1909
• Bohr model of the atom

  1913
• Before the discovery of the electron, John Dalton said atoms were solid balls that could not be divided
• Thompson's experiments showed that an atom must contain small negative charges (discovery of electrons)
• Ernest Rutherford's alpha particle scattering experiment showed that most of the mass of an atom was at its centre
• Niels Bohr proposed that electrons orbited in fixed shells; this was supported by experimental observations
• James Chadwick provided the evidence to show the existence of neutrons within the nucleus
• Methods of separating mixtures

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Chemical equation


  Shows how chemical reactions change reactants into products, and usually involves an energy change
• Balanced chemical equation


  Shows the number of atoms and molecules in the reaction, which need to be balanced
• Law of conservation of mass


  States the total mass of products must equal the total mass of reactants
• Isotopes


  Atoms of the same element with the same number of protons and different numbers of neutrons
• Relative atomic mass


  Calculated from the masses and percentages of the isotopes of an element
• Groups in the periodic table

  • Group 1 - Alkali metals
  • Group 7 - Halogens
  • Group 0 - Noble gases
• Metals


  • Form positive ions, are conductors, have high melting and boiling points, are ductile and malleable
• Non-metals


  • Form negative ions, are insulators, have low melting and boiling points
• Halogens


  Group 7 elements that form molecules containing a pair of atoms
• Reactivity of halogens


  Decreases down the group
• Melting and boiling points of halogens

  Increase down the group (gas at the top, then liquid, then solid)
• Atomic mass of halogens


  Gets heavier as you go down the group
• Reactivity of Group 1 elements

  Increases as you go down the group
• Reactions of Group 1 elements

  1. Form metal oxides

  2. Form metal hydroxides and hydrogen

  3. Form metal chlorides
• Group 0 elements


  • Very unreactive, don't form molecules
• Boiling points of Group 0 elements

  Increase as you go down the group
• Giant covalent structures


  Structures where all atoms are linked by strong covalent bonds, e.g. diamond, graphite, silicon dioxide
• Properties of giant covalent structures

  • High melting/boiling points, do not conduct electricity
• Covalent molecular structures


  Structures where atoms share pairs of electrons to form covalent bonds within small molecules
• Properties of covalent molecular structures

  • Usually gases or liquids, low melting and boiling points, do not conduct electricity
• Polymers


  Very large molecules containing atoms linked by strong covalent bonds