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The Periodic Table

The Periodic Table. The most important document in chemistry. Learning objectives. Define group and period as related to periodic table Describe properties of metal, semi-metal and nonmetal Write names and symbols of several common elements

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The Periodic Table

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  1. The Periodic Table The most important document in chemistry

  2. Learning objectives • Define group and period as related to periodic table • Describe properties of metal, semi-metal and nonmetal • Write names and symbols of several common elements • Predict type of element from position in periodic table

  3. Elements: names and symbols • All elements have a name and a symbol (one or two letters) • Symbols are used in writing compound formulae and chemical equations • It is essential to be familiar with both names and symbols for the important elements

  4. Common elements and symbols - obvious • Carbon • Calcium • Chlorine • Nitrogen • Oxygen • Aluminium • Phosphorous

  5. Common elements and symbols – less obvious • Sodium • Potassium • Iron • Mercury • Silver • Gold • Tungsten

  6. 1869Dimitri Mendeleev developed the periodic table • Ordered elements according to atomic weights and physical and chemical properties. • Only about 60 elements had been identified • Predicted existence of as-yet-undiscovered elements and their properties. Predictions often proved astonishingly accurate.

  7. The modern periodic tableThere are 92 naturally occurring elements: 2 liquids, 11 gases, 23-25 nonmetals

  8. Reduce chemistry of all elements to discussion of group behaviour • 1A ALKALI METALS: Reactive. Reactivity increases down group. Physical properties vary gradually. • 2A ALKALINE EARTH METALS : Similar to alkalis but less reactive. Lots of common calcium compounds: calcium carbonate (limestone, marble), calcium oxide (lime), calcium sulphate (gypsum, plaster of Paris)

  9. Important groups on other side of table • 7A HALOGENS: Very reactive, form lots of compounds with most elements. Chlorides in particular are common: NaCl, KCl. Reactivity decreases down group • 8A RARE, INERT, NOBLE GASES: Discovered late because of lack of compounds, all gases. Not “rare” since 1 % argon in air; He second most abundant element in universe. Very unreactive. Provide insight into properties of other elements

  10. The Periodic Table: two main types of element: metals -are shiny, lustrous; good conductors of heat and electricity. Only one metal is a liquid at room temp.

  11. The Periodic Table: non-metals - insulators (or perhaps semiconductors), poor heat conductors mostly. Solids are brittle. Several are gases, one is a liquid.

  12. The Periodic Table: semi-metals – borderline cases • Some properties are metal-like • Other properties are nonmetal-like • Semiconductors

  13. Atoms and ions • Ions are charged particles with more or less electrons than protons • Positive ion (cation) has fewer electrons • Negative ion (anion) has more electrons

  14. Ions and compounds • Ions are important in one class of compounds • Metals form positive ions • Nonmetals form negative ions • Periodic table can be used to predict charges

  15. Rules to predict ion charge • Cation • Charge = group number • Anion • Charge = - (8 - group number) • Practice with a few examples

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