Chem 1

• The number of protons is equal to the atomic number
• Element

  A substance containing only one type of atom
• Chemical reaction

  Causes atoms to change what they're bonded to
• Compound

  A substance containing two or more different types of atoms chemically bonded
• Due to conservation of mass, atoms can neither be created nor destroyed in a chemical reaction
• Balancing chemical reaction equations


  1. Start with atoms in a compound, end with elements

  2. Only put numbers in front of substances to balance the equation
• Mixture

  Different substances NOT CHEMICALLY BONDED e.g. air, solutions
• Filtration


  • Removes large, insoluble particles from a liquid e.g. sand from water
• Evaporation


  • Leaves behind crystals of a dissolved substance (solute) if heated gently
• Chromatography

  Causes substance to rise up paper due to CAPILLARY ACTION, lighter particles move further up
• Distillation

  • Involves condensing the evaporated solvent and collecting it
• Fractional distillation


  • Can separate liquids due to their different boiling points
• Solid


  • Particles in regular arrangement (lattice) and vibrate about fixed positions
  • Cannot be compressed
  • Particles have no regular arrangement and are able to move and pack each other
• Liquid

  • Particles can be compressed
  • Particles move randomly at fast speeds (high energy)
• Gas

  • Particles are far apart
  • Particles move randomly at fast speeds (high energy)
  • Can be compressed
• Physical change: no new substance made
• State symbols

  • Can be used in an equation
  • (aq) indicates the substance is in solution ('aqueous)
• Energy (heat) is needed to overcome the (electrostatic) forces of attraction between particles to melt/evaporate
• Atomic model


  • Developed over time
• Atomic model development


  • Ancient Greeks thought matter to be made of indivisible particles
  • Thomson created the plum pudding model
  • Rutherford discovered the nucleus is positively charged and most alpha particles went straight through a gold leaf
  • Bohr deduced electrons exist in shells
  • Chadwick determined the nucleus contains neutrons as well as protons
• Proton

  Positively charged particle in the nucleus
• Neutron

  Neutral particle in the nucleus
• Electron

  Negatively charged particle orbiting the nucleus
• Protons have a relative charge of +1, neutrons have a relative charge of 0, and electrons have a relative charge of -1
• MASS NUMBER (or RELATIVE ATOMIC MASS/RAM/A)

  The number of PROTONS+NEUTRONS in a nucleus
• ATOMIC NUMBER

  The number of PROTONS in a nucleus
• An ATOM must also have the same number of ELECTRONS as PROTONS in order to be neutral. If not, it is an ION instead.
• Elements in periodic table ordered according to atomic weight
• Metals

  Always donate electrons to gain an empty outer shell and form positive ions (e.g. Na+)
• Non-metals

  Always accept electrons to gain a full outer shell. They can form negative ions (e.g. O-) or share electrons.
• Hydrogen

  Can basically do both (donate or accept electrons)
• Transition metals are a bit more complicated, but they still form positive ions
• Transition metals

  Can donate different numbers of electrons e.g. an IRON (II) ion is Fe2+, while IRON (I) is Fe+
• Group 1

  • Alkali metals
  • They react with water to produce an alkali
  • They all lose/donate their outer electron to their ions which are all (1+) e.g. Na+
• Down the group

  Alkali metals get more reactive
• Group 7

  • Halogens
  • They form (1-) ions as they accept 1 electron to gain a full outer shell
  • They get less reactive down the group (and boiling point increases)
• Group 0/8

  • Noble gases
  • They are VERY UNREACTIVE as they already have an empty outer shell
• Ionic bonding

  How metals bond to non-metals
• Ionic bonding

  1. Metal atoms donate electrons

  2. Non-metals accept electrons

  3. Ions are formed
• Dot & cross diagrams


  Show the electrons on the outer shells