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Topic 3: Periodicity

3.1 Periodic Table
Essential Idea:
  • The arrangement of elements in the periodic table helps to predict their electron configuration.
  • The periodic table is arranged into four blocks associated with the four sub-levels—s, p, d, and f.
  • The periodic table consists of groups (vertical columns) and periods (horizontal rows).
  • The period number (n) is the outer energy level that is occupied by electrons.
  • The number of the principal energy level and the number of the valence electrons in an atom can be deduced from its position on the periodic table.
  • The periodic table shows the positions of metals, non-metals and metalloids.
Applications & Skills:
  • Deduction of the electron configuration of an atom from the element’s position on the periodic table, and vice versa.
Nature of Science:
  • Obtain evidence for scientific theories by making and testing predictions based on them—scientists organize subjects based on structure and function; the periodic table is a key example of this. Early models of the periodic table from Mendeleev, and later Moseley, allowed for the prediction of properties of elements that had not yet been discovered.
PPT: 3.1 Periodic Table
3.2 Periodic Trends
Essential Idea:
  • Elements show trends in their physical and chemical properties across periods and down groups.
  • Vertical and horizontal trends in the periodic table exist for atomic radius, ionic radius, ionization energy, electron affinity and electronegativity.
  • Trends in metallic and non-metallic behaviour are due to the trends above.
  • Oxides change from basic through amphoteric to acidic across a period.
Applications & Skills:
  • Prediction and explanation of the metallic and non-metallic behaviour of an element based on its position in the periodic table.
  • Discussion of the similarities and differences in the properties of elements in the same group, with reference to alkali metals (group 1) and halogens (group 17).
  • Construction of equations to explain the pH changes for reactions of Na2O, MgO, P4O10, and the oxides of nitrogen and sulfur with water.
Nature of Science:
  • Looking for patterns—the position of an element in the periodic table allows scientists to make accurate predictions of its physical and chemical properties.
  • This gives scientists the ability to synthesize new substances based on the expected reactivity of elements.
PPT: 3.2 Periodic Trends
Periodic Properties Lab