chemistry paper 1

• Substances are made of atoms
• Element

  A type of atom represented in the periodic table by a symbol
• Compound

  A substance that contains two or more different types of atoms chemically bonded together
• If there's no number after a symbol, there's an invisible 1
• Chemical reaction

  Atoms change what they're bonded to and how they're bonded
• Word equation


  A representation of a chemical reaction using words
• Chemical equation


  A representation of a chemical reaction using symbols
• Atoms are not created or destroyed in any chemical reaction, so the same number of each type of atom must be on both sides of the equation</b>
• Balancing a chemical equation

  Start with atoms only in compounds, then balance remaining atoms
• Mixture


  Any combination of different types of elements and compounds that aren't chemically bonded together
• Solution


  A mixture of a solute dissolved in a solvent
• Filtration


  Separating large insoluble particles from a liquid
• Crystallization


  Leaving a solute behind after evaporating the solvent from a solution
• Distillation


  Separating liquids with different boiling points by heating the solution and condensing the vapour
• Filtration, crystallization, and distillation are physical processes, not chemical reactions
• States of matter


  Solid, liquid, gas
• Water can exist as a solid (ice), liquid, or gas (water vapour)
• Melting and evaporation


  Require energy (usually heat) to overcome the electrostatic forces of attraction between particles
• Melting and evaporation are physical changes, not chemical reactions
• Plum pudding model of the atom

  Proposed by JJ Thompson, with a positive charge and electrons dotted around it
• Rutherford's model of the atom

  Discovered the positive charge is in a small nucleus, with electrons orbiting relatively far away
• Bohr's model of the atom


  Electrons exist in shells or orbitals around the nucleus
• Protons and neutrons


  Positive and neutral charges respectively in the nucleus
• Electrons


  Negative charges orbiting the nucleus
• Atomic number


  Number of protons in the nucleus, determines the element
• Mass number

  Total number of protons and neutrons in the nucleus
• Isotopes


  Atoms of the same element with different numbers of neutrons
• Relative abundance


  The percentage of each isotope in a sample
• The periodic table was originally ordered by atomic weight, then rearranged by Mendeleev based on chemical properties
• Electron configuration


  The arrangement of electrons in shells around the nucleus
• Sections of the periodic table

  • Metals (left of staircase)
  • Non-metals (right of staircase)
• Group

  The column an atom is in, indicates number of outer shell electrons
• Alkali metals

  Group 1 elements, have 1 outer electron to donate
• Halogens


  Group 7 elements, need 1 electron to fill outer shell
• Noble gases

  Group 0 elements, have full outer shells and are very unreactive
• Ion


  An atom that has gained or lost electrons, no longer electrically neutral
• Transition metals


  Can form ions with different charges
• Metallic bonding

  Atoms bonded in a lattice with delocalized electrons
• Ionic bonding


  Metal atoms donate electrons to non-metal atoms to form ions
• Covalent bonding


  Non-metal atoms share electrons to fill their outer shells