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. 1869 Dimitri 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 table There 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