1. Atomic Structure and the Periodic Table

• Atoms


  Incredibly small, make up everything in the universe, smallest part of an element that can exist
• Atoms


  • Composed of three sub-atomic particles: protons, neutrons, and electrons
• Nucleus


  Center of an atom, containing protons and neutrons
• Protons


  Positive charge (+1), relative mass of 1
• Neutrons


  No charge (0), relative mass of 1, similar to protons
• Electrons


  Negatively charged (-1), very small, with virtually no mass when compared to protons and neutrons
• The nucleus is tiny compared to the whole atom, about 1/10,000th of the atom's total size, but it holds nearly all the atom's mass
• Radius of an atom

  0.1nm (1 x 10 -10 m)
• Radius of a nucleus

  1 x 10 -14 m
• Atoms are neutral and have no overall charge because they have the same number of protons and electrons, which cancels out their charges
• Chemical symbol


  Atoms of each element is represented by a symbol which can be found in the periodic table
• Atomic number


  Indicates how many protons are in an atom's nucleus
• Mass number


  Total count of both protons and neutrons
• To find the number of neutrons


  Subtract the atomic number from the mass number
• Element


  A substance made up of one type of atom
• There are over 100 different discovered elements which can all be found in the periodic table
• All the atoms in an element contain the same number of protons in their nucleus
• When atoms have different numbers of protons, they are classified as different elements
• Isotopes


  Different forms of the same element, having the same number of protons (same atomic number) but different numbers of neutrons (different mass numbers)
• Compound


  Substances that form when two or more elements react and their atoms combine in fixed proportions, held together by chemical bonds
• In compounds, only the electrons are involved in bond formation while the nuclei remain unchanged
• The properties of a compound are usually quite different from the properties of the original elements
• Compound formula


  Represents compounds and shows the elements and the number of atoms of each element in a compound
• Relative atomic mass (Ar)


  The average mass of all the isotopes of an element, taking into account their abundance
• Abundance


  How common a particular isotope is
• To calculate the relative atomic mass


  Use the formula: (Abundance of isotope 1 x Mass of isotope 1) + (Abundance of isotope 2 x Mass of isotope 2) + ...
• Chemical equation


  Used to show what happens during a chemical reaction, with the left hand side representing the reactants and the right hand side representing the products
• Word equation


  Expresses the reactants and products of a reaction in words
• Symbol equation


  More concise, using chemical symbols and formulas to represent the reactants and products
• Symbol equations must be balanced, meaning they have the same number of each type of atom on both sides of the equation
• Steps to balance equations

  Identify the number of atoms of each element on either side of the equation

  2. Adjust the coefficients to balance that element, which may cause another element to become unbalanced

  3. Repeat the process, adjusting coefficients as necessary until the equation is balanced
• Mixture


  Combinations of two or more substances that are not chemically combined
• Compound


  Combinations of two or more substances that are chemically combined
• Compounds can only be separated using chemical reactions, while mixtures can be separated using physical methods
• Examples of physical separation techniques


  • Filtration
  • Evaporation
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Filtration


  A method used to separate an insoluble solid from a liquid
• Evaporation


  A method to recover soluble solids like salt by dissolving them in a solvent and then evaporating the solvent
• Crystallisation


  A method to recover soluble solids by dissolving them in a solvent, heating to form a saturated solution, and then allowing the solution to cool to form crystals
• Simple distillation


  A process to separate a liquid from a solution, often used when the liquids have different boiling points
• Fractional distillation


  Used to separate a mixture of more than two liquids that have different boiling points, using a fractionating column to create a temperature gradient