- The document discusses atoms, ions, molecules, elements, compounds, and chemical formulas and reactions. - Atoms combine to form molecules, and molecules made of the same type of atom are elements, while molecules with different atom types are compounds. - Chemical formulas use symbols and subscripts to represent the elements and number of each type of atom in a molecule or compound. - Chemical reactions can release or absorb energy and are classified as exothermic or endothermic respectively.

1. Do NOT make an ATOM an ION unless it tells you too! THIS MEANS- Do NOT make an ATOM stable unless it tells you to do so . To determine the charge of a picture of an atom look at the number of protons and electrons in the picture and determine the charge. (Examples are on the next slide.)

2. Review: What is the charge of this ATOM ? Just use the number of protons and electrons that are given .

3. What is the charge of this ATOM? Just use the number of protons and electrons that are given. -2

4. We will discuss: Chemical Symbol Atoms Elements Bonds Compounds Molecules Chemical Formulas Endothermic Reactions Exothermic Reactions

7. 6 C 12 Chemical Symbol

9. Molecules form when atoms join Element Compound There are two types of molecules

11. Molecules Element H 2 If all atoms in a molecule are alike, then the molecule is classified as an _______________. ELEMENT

12. Molecules form when atoms join Compound The other type of molecule is a compound. Do you think that the atoms joined together in a compound are all the same? NO! The atoms are different.

15. Chemical Formulas- represent a molecule O C O The chemical formula of this model is CO 2

19. CO represents? Co represents? Fe O represents? 2 3 1 atom of carbon and 1 atom of oxygen 1 atom of cobalt 2 iron atoms and 3 oxygen atoms