2. Chemical Formula

3. atom molecule compound ex: H 2 0, NaCl element O O 2 matter

4. symbol - p 20 usually 1 or 2 letters that are used to identify an element only 1st letter is capitalized (ex: He - helium)

5. symbolhydrogenH

6. Co CO Co - cobalt CO - carbon, oxygen

7. formula - p 20 a combination of symbols that shows the ratio of elements in a compound Ex: H 2 O, the ratio of Hydrogen to Oxygen is 2:1Ex: H 2 O, the ratio of Hydrogen to Oxygen is 2:1

8. formula

9. Example (add to notes on formula) CH 4 (methane)CH 4 (methane) 1:4 ratio1:4 ratio 1 Carbon atom: 4 Hydrogen atoms1 Carbon atom: 4 Hydrogen atoms

14. copper + oxygen → copper oxide Word Equations A word equation gives the names of the substances involved in a reaction. For example: copper + oxygen → copper oxide Copper and oxygen are the reactants, and copper oxide is the product.

15. Cu + O 2 → CuO Chemical Equations Chemical equations give the symbols and molecular formula of the substances involved in a reaction. In the example below, if we just replace the words shown below with the correct chemical formula, we will get an unbalanced equation, as shown here: copper + oxide yields copper oxide Cu + O 2 → CuO

16. Chemical equations give the symbols and molecular formula of the substances involved in a reaction. In the example below, if we just replace the words with the correct chemical formula, we will get an unbalanced equation, as shown here: Copper + oxygen yields copper oxide Cu + O 2 → CuO To make things equal, we need to adjust the number of units of some of the substances until we get equal numbers of each type of atom on both sides of the arrow. Here is the balanced chemical equation: 2Cu + O 2 → 2CuO

17. 2Cu + O 2  2CuO

22. atoms two Elements compounds fewer larger

23. three three 10 21 more than a billion

24. b c e a d

25. 2sulfur oxygen 1 2 3 2 nitrogen hydrogen 1 3 4

26. 6 45 6 3 4 hydrogen carbon oxygen hydrogen oxygen carbon hydrogen oxygen magnesium sulfur oxygen sodium oxygen hydrogen 3 2 1 3 12 22 11 1 1 1 1 1 4 2 2 3 3 2 3

27. 5 6 2 4 iron oxygen 2 3 1 1 1 3 sodium hydrogen carbon oxygen