C1 Atomic Structure

• What is an atom?

  Smallest part of an element
• What is an element?


  A substance made up of only one type of atom
• Atom


  The smallest part of an element that can exist
• Element


  A substance of only one type of atom
• Elements are listed in the periodic table; there are approximately 100
• Compounds


  New substances formed when elements combine through chemical reactions
• 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


  A mixture consists of 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
• Methods to separate mixtures do not involve chemical reactions
• Simple distillation


  1. Separate liquid from solution

  2. Liquid boils off

  3. Condenses in condenser

  4. Thermometer reads boiling point
• Crystallisation/Evaporation


  1. Heat solution to evaporate solvent

  2. Remove some solvent to form saturated solution

  3. Cool down solution

  4. Collect crystals via filtration
• Fractional distillation


  1. Separate mixture of liquids

  2. Different boiling points

  3. Use fractionating column

  4. Condense at different heights
• Filtration


  1. Separate insoluble solid from liquid

  2. Residue caught in filter paper

  3. Filtrate comes through filter paper
• Chromatography


  1. Separate mixture of substances in solvent

  2. Place paper with mixture in solvent

  3. Solvent rises and separates components
• Separating funnel


  An apparatus for separating immiscible liquids
• Plum-pudding model


  The atom is a ball of positive charge with negative electrons embedded in it
• Nuclear model


  Electrons orbit the nucleus at specific distances (shells)
• The nuclear model came about from the alpha scattering experiments
• Protons


  Smaller, positive particles in the nucleus
• Neutrons


  Particles in the nucleus discovered by James Chadwick
• Structure of an atom

  Small central nucleus made up of protons and neutrons around which there are electrons
• Relative masses and charges

  • Proton: mass 1, charge 1
  • Neutron: mass 1, charge 0
  • Electron: mass very small, charge -1
• Atoms are electrically neutral because they have the same number of electrons and protons
• Atomic number


  The number of protons in the nucleus
• Atoms are electrically neutral
• Atoms of the same element

  Have the same number of protons in the nucleus
• Mass number


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


  Subtract atomic number from mass number
• Isotope


  Atoms of the same element (same proton number) that have a different number of neutrons
• 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: 2,2
  • F: 2,7
  • Na: 2,8,1
  • Ca: 2,8,8,2
• Ions


  Charged particles formed when atoms lose or gain electrons
• Example of a positive ion


  • Sodium positive ion, Na+
• Sodium positive ion has an electronic configuration of 2,8
• Properties of metals


  • High boiling/melting point
  • Conduct heat and electricity
  • Shiny
  • Malleable
  • High density
  • Basic oxides
• Properties of non-metals


  • Low boiling/melting point
  • Don’t conduct heat, electricity (with exception of graphite)
  • Dull
  • Brittle
  • Low density
  • Acidic oxides
• Solute


  A substance that is dissolved in a solvent