Chemistry atomic structure and the periodic table

• Atom


  The smallest part of an element that can exist
• Element


  A substance of only one type of atom
• There are approximately 100 elements listed in the periodic table
• Groups of elements based on properties

  • Metals
  • Non-metals
• Compound


  Two or more elements combined chemically in fixed proportions which can be represented by formulae
• Compounds have different properties than their constituent elements
• Mixture


  Two or more elements or compounds not chemically combined together
• Mixtures have the same chemical properties as their constituent materials
• Methods to separate mixtures

  • Filtration
  • Crystallisation
  • Simple distillation
  • Fractional distillation
  • Chromatography
• Separation methods for mixtures do not involve chemical reactions
• Simple distillation


  1. Liquid boils off and condenses in the condenser

  2. Thermometer reads the boiling point of the pure liquid
• Crystallisation/Evaporation


  1. Solution is heated until all the solvent evaporates

  2. Solids stay in the vessel

  3. Saturated solution is cooled to form crystals
• Fractional distillation


  1. Mixture is repeatedly condensed and vaporised in a fractionating column

  2. Liquids condense at different heights in the column
• Filtration


  1. Insoluble solid (residue) gets caught in the filter paper

  2. Filtrate is the substance that comes through the filter paper
• Chromatography


  1. Mixture is dissolved in a solvent and placed on paper

  2. Solvent rises up the paper, separating the mixture
• Separating funnel


  Apparatus for separating immiscible liquids of different densities
• Plum-pudding model


  Atom is a ball of positive charge with negative electrons embedded in it
• Bohr/nuclear model


  Electrons orbit the nucleus at specific distances (shells), came from alpha scattering experiments
• Later experiments led to the discovery of protons in the nucleus
• James Chadwick's work provided evidence for the existence of neutrons in the nucleus
• Atom structure


  Small central nucleus (protons and neutrons) with electrons orbiting
• Protons and neutrons have a mass of 1, electrons have a very small mass
• Protons have a charge of 1, neutrons have a charge of 0, electrons have a charge of -1
• Atoms are electrically neutral because they have the same number of electrons and protons
• The radius of an atom is 0.1 nm
• The radius of a nucleus is 1 x 10-14 m, which is 1/10000 the radius of the atom
• Number of protons in the nucleus

  Atomic number
• Atoms are electrically neutral
• Atoms are electrically neutral because


  They have the same number of electrons and protons
• Radius of an atom

  0.1 nm
• Radius of a nucleus

  1 x 10-14 m
• Atoms of the same element have the same number of protons in the nucleus
• Where the majority of mass of an atom is

  The nucleus
• Mass number


  The total number of protons and neutrons
• Calculating the number of neutrons


  Subtract the atomic number from the mass number
• Isotope


  Atoms of the same element (same proton number) that have a different number of neutrons. They have the same chemical properties as they have the same electronic structure.
• Relative atomic mass


  The average mass value which takes the mass and abundance of isotopes of an element into account, on a scale where the mass of 12C is 12.
• Ions


  Charged particles formed when atoms lose (positive ions) or gain (negative ions) electrons
• Comparison of properties of metals and non-metals

  • Boiling/melting point (High/Low)
  • Conductivity (Heat and electricity/Don't conduct heat, electricity (with exception of graphite))
  • Appearance (Shiny/Dull)
  • Malleability (Yes/Brittle)
  • Density (High/Low)
  • Oxides (Basic/Acidic)
• Reaction between metal and non-metal

  Forms an ionic compound