chemistry

• Compound

  A substance that contains two or more different types of atoms chemically bonded together
• Atoms change what they're bonded to and how they're bonded through chemical reactions
• Word equation


  A way to represent a chemical reaction
• Chemical equation


  A way to represent a chemical reaction using symbols
• Atoms are not created or destroyed in any chemical reaction.

  there must be the same number of each type of atom on both sides.
• Balancing a chemical equation

  1. Start with atoms only in compounds

  2. Balance carbons

  3. Balance hydrogens

  4. Balance other elements by putting numbers in front
• Mixture


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


  A mixture of a solute dissolved in a solvent
• Separating mixtures


  1. Filtration (for large insoluble particles)

  2. Crystallization (to leave a solute behind after evaporating the solvent)

  3. Distillation (to separate liquids based on different boiling points)
• Physical processes


  • Do not create new substances, only separate existing ones
• States of matter


  • Solid (particles vibrate around fixed positions)
  • Liquid (particles can move past each other)
  • Gas (particles are far apart and move randomly)
• Melting and evaporation require energy to overcome electrostatic forces of attraction between particles
• Chemical reactions involve breaking and forming chemical bonds, unlike physical changes
• Atomic models


  • JJ Thompson's plum pudding model
  • Rutherford's discovery of the nucleus and mostly empty space
  • Bohr's discovery of electron shells/orbitals
  • Chadwick's discovery of neutrons
• Atomic number


  The number of protons in the nucleus
• Mass number


  The total number of protons and neutrons in the nucleus
• Isotopes


  Atoms of the same element with different numbers of neutrons
• The periodic table was originally ordered by atomic weight, then later by properties and predicted gaps
• Electron configuration


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

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


  The column an atom is in on the periodic table, indicates number of outer shell electrons
• Groups

  • Group 1 (alkali metals)
  • Group 7 (halogens)
  • Group 0 (noble gases)
• Ion

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

  • Can have variable charges (e.g. Fe2+ or Fe3+)
• Metallic bonding

  Bonding in metals, with a lattice of positive ions and delocalized electrons
• Ionic bonding

  Bonding between a metal and a non-metal, with transfer of electrons
• Covalent bonding

  Bonding between non-metals, by sharing electrons
• Molecular ion

  An ion formed from a group of atoms, e.g. OH-
• Ionic compound

  A compound made up of positive and negative ions in a lattice structure
• Simple molecular structure

  Individual molecules that can mix together, with relatively low boiling points
• Giant covalent structure


  A continuous network of covalent bonds, e.g. diamond and graphite
• Nanoparticles have a very high surface area to volume ratio compared to larger particles
• Mole


  A specific number of atoms or molecules, used to compare amounts of substances
• The atoms that go in must come out in a chemical reaction, so we must balance equations
• Relative formula mass


  The sum of the relative atomic masses of the atoms in a compound
• Some reactions produce a gas product which, if it leaves the reaction vessel, will result in a seeming decrease in mass of the reactants
• Mole


  A specific number of atoms or molecules, used as a way of comparing amounts of substances
• One mole

  The amount of a substance that has a mass equal to its relative atomic or formula mass in grams
• In a balanced chemical equation, the ratio of moles of reactants to products is the stoichiometry
• Calculating mass of product from mass of reactant

  Mass -> Moles -> Moles -> Mass