Unit 1A ACS Chemistry in the Community Sixth Edition

1. Unit 1A ACS Chemistry in the Community Sixth Edition

2. Chemical Symbols and Formulas Unit 1.A.6 and 7

5. Chemical Symbols • All elements in the Periodic Table have symbols that are recognized world wide. • It does not matter which country you are in or the language you speak. • Example: The element Iron is always identified by “Fe” and Oxygen is “O”. • The names are not always the same but the symbols are. “Fe” is iron in Canada, fer in France and fier in Romania.

7. Chemical Symbols A Chemical symbol is an abbreviation of a name of an element. Capital letter if only one letter. Only first letter capital if more than one letter

8. Sodium comes from the word sodanum, a headache remedy, and it’s symbol (Na) comes from the Latin word Natrium.

9. Chemical Formulas A chemical formula is the combination of symbols that represent a particular compound. The chemical formula indicates which elements are present in the compound and in what proportions. Ex. 1: Water molecule H2O: 2 atoms of hydrogen, 1 atom of oxygen Ex. 2: Iron Oxide molecule Fe2O3: 2 atoms of iron, 3 atom of oxygen

10. Chemical Formulas - Examples • Calcium Carbonate (chalk) – CaCO3 • Sodium Chloride (salt) – NaCl • Acetysalicylic acid (aspirin) – C9H4O8 • Acetic acid (vinegar) – C2H4O2

11. Chemical Formulas • NOTES: - Each symbol in a formula represents an element. - If only one atom of an element is present in the compound, no subscript is used. - If more than one atom of an element is used, then the symbol is followed by a number indicating how many atoms are used. This is called the subscript.

13. Chemical Reactions

14. I. CHEMICAL EQUATIONS A. Definitions 1. Chemical Equation - represents reactants and products in a reaction using symbols, formulas and coefficients. 2. Subscript - indicate the number of atoms of an element in a chemical reaction. 3. Coefficient - whole number in front of a formula or symbol that indicates the number of atoms, molecules, formula units or moles

15. Subscripts vs. Coefficients • The subscripts tell you how many atoms of a particular element are in a compound. The coefficient tells you about the quantity, or number, of molecules of the compound.

16. CHEMICAL REACTIONS Reactants: Zn + I2 Product: Zn I2

17. Methods for Writing Equations 1. word equation – reactants and products are represented by words 2. formula equation- reactants and products are represented by element symbols and formulas 3. balanced chemical equation – a formula equation using coefficients to represent the number of atoms, molecules, or formula units

18. Symbols Used in Writing Equations 1. --------> yields, forms, produces, reacts to form 2. --------> reversible reaction (products <--------- react to re-form the reactants) 3. symbols or words written above -----> a.triangle– reaction requires heat b. oC– indicates temperature required c. atm– indicate pressure is required d. symbol for element or formula for compound – catalyst is required

19. letters or symbols next to formula a. letters (s) – solid (l) – liquid (g) – gas (aq) – aqueous solution b. symbols arrow point up – gas produced arrow pointingdown–precipitate forms

20. Chemical Equations 4 Al(s) + 3 O2(g) ---> 2 Al2O3(s) This equation means 4 Al atoms + 3 O2 molecules ---produces---> 2 molecules of Al2O3 AND/OR 4 moles of Al + 3 moles of O2 ---produces---> 2 moles of Al2O3

21. http://www.youtube.com/watch?v=d58UcB_Yb2Q • 1.  Define the terms “reactants” and “products.” Give examples of each from a chemical equation. • 2. What do all chemical reactions need? • 3. What do you think EA stand for? • 4. What role does a catalyst play in a chemical reaction?

22. CHEMICAL REACTIONS • Bonds and Chemical Reactions 1. bonds form, break or both 2. atoms combine, separate, rearrange A + B  A-B C-D  C + D A-B + C  C-B + A C-D + B  C-B + D A-B + C-D  A-D + C-B