1. CHEMICAL FORMULAS

2. Chemical Formulas  A chemical formula provides the clearest and simplest method of designating compounds.  It indicates the number and kind of elements present in the compound.  Compounds that consist of two elements are called binary compounds.

3. Binary Compounds  AlCl 3  NaCl  MgO  CO 2  LiH

4. General Rules for Oxidation Numbers  Charge on pure elements is _______.  All metals of Group IA are ________.  All metals of Group IIA are _______.  The charge on all elements in Group IIIA is _____ except Tl which can also be ____.  The charge on hydrogen is ___or __.  The charge on fluorine is ____.

5. General Rules for Oxidation Numbers 7. Other halogens (VIIA) are ____ except when combined with oxygen. Then they are +. 8. Group IVA elements are ___ when negative. 9. Group VA elements are ____ when negative. 10. Group VIA elements are ___ when negative.

6. Polyatomic Ions Memory Work AAmmonium_______Cyanide_________ AAcetate__________Carbonate_______ NNitrate__________Sulfate__________ HHydroxide_______Phosphate________

7. Writing Formulas of Compounds 1.Write the symbol for the positive element first.  The element name with the ending changed to -ide indicates the element with a negative oxidation number.

8. Writing Formulas of Compounds  Examples:  Oxide = ________telluride = ________  Chloride = ______hydride = ________  __________ = S 2- __________ = P 3-

9. Writing Formulas of Compounds  Use subscripts to make the formula contain the number of atoms required for a neutral formula unit. Example:sodium chloride Na 1+ Cl 1- 1+1- = 0 NaCl

10. Writing Formulas of Compounds  calcium chloridesodium oxide

11. Writing formulas of compounds  Magnesium nitridepotassium hydride

12. Writing formulas of compounds  If more than one polyatomic ion appears in the formula put the polyatomic ion in parentheses. Example: potassium nitrate

13. Writing formulas of compounds  Magnesium nitrate

14. Writing formulas of compounds  If a Roman numeral appears after the name of the positive element, this number indicates the oxidation number of the positive element. Example: tin (IV) chloride

16. Naming Binary Compounds  State the name of the positive element first.  State the name of the negative element and change the ending to -ide.  NaCl sodium chloride  CaS _____________

17. Naming Binary Compounds  If the positive element can have more than one positive oxidation number use the stock system:  Stock System- Put a Roman numeral in parentheses after the name of the positive element to show its oxidation number.

18. Naming Binary Compounds  CuCl 2  Note: Do not use the Stock System if only one positive oxidation number is possible.

19. Naming Compounds that contain Polyatomic Ions  Write the name of the positive element first.  If the positive element has more than one possible oxidation number use the stock system.  The names and formulas of polyatomic ions are generally to be memorized.

20. Examples

21. Greek Prefix System  An older system of nomenclature is often used, especially for compounds containing only nonmetals.  Greek prefixes are used to tell how many atoms are present in the formula.