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
• The elements are listed in the periodic table; there are approximately 100
• 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
• Masses: proton 1, neutron 1, electron very small; Charges: proton 1, neutron 0, electron -1
• Atoms are electrically neutral because they have the same number of electrons and protons
• Radius of an atom is 0.1 nm
• Radius of a nucleus is 1 x 10-14 m, which is 1/10000 of the atom radius
• Number of protons in the nucleus

  Atomic number
• Atoms are electrically neutral


  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
• Majority of mass of an atom

  The nucleus
• Mass number


  The total number of protons and neutrons
• Calculating 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.
• Electronic configurations


  • He (2), Be (4), F (9), Na (11), Ca (20)
• Ion


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

  • Boiling/melting point (high/low), Conductivity (heat and electricity/don't conduct), Appearance (shiny/dull), Malleability (yes/brittle), Density (high/low), Oxides (basic/acidic)
• Product of metal and non-metal reaction

  Ionic compound
• Product of non-metal and non-metal reaction

  Molecular compound containing covalently bonded atoms