- 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

5. All matter is made of _____________. Atoms Why would an atom combine with other atoms? To make the atom stable When an atom combines with another atom, this forms a ______________________? Molecule

6. When atoms are joined together, they form a _____BOND______. Atoms bond together for a very simple reason: atoms like to have full valence shells . (8 electrons) Atoms will share, give away, or gain electrons when forming a bond. Substances in which 2 or more elements have bonded together form a material with unique chemical properties. Example : water - 2 Hydrogen atoms bonded to 1 Oxygen atom. H2O

7. 6 C 12 Chemical Symbol

8. Molecules Are made of ______________ that have been joined together. ATOMS

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

10. Element Molecule Element If a substance has two or more of the same atoms it is a molecule that is an Element Ex. O (the oxygen we breathe) is made out of two oxygen atoms Other examples of Element Molecules: H N O 2 2 3 3

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.

13. Compound Molecules A combination of two or more different elements (atoms) Examples: 1 Na atom + 1 Cl atom = the compound NaCl 2 H atoms + 1 O atom = the compound H O The examples above are compounds because the molecule is made out of _____________ atoms. 2 DIFFERENT

14. Energy in Chemical Reactions Often energy is released or absorbed in chemical reactions. Where does the energy come from?? Bonds break or form from electrons being lost or gained. Energy is released when there is less energy in the products than the reactants. This is called an EXOTHERMIC reaction. If energy is absorbed there is less energy in the reactants than the products. This is called an ENDOTHERMIC reaction. Exo = out Endo= in

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

16. CO Chemical Formula 2 C Chemical Symbol

17. The Chemical Formula use symbols and numbers called subscripts to show the elements and number of atoms that make up the molecule. H O 2 Chemical Symbols Subscript Note: there are 2 hydrogen atoms and 1 oxygen atom. The one behind the O is imaginary. How many atoms are there? _____ 3

18. H O Tells Us: There are ______ atoms of hydrogen and _____ atoms of oxygen. The name of the elements which are ____________ and ______________. 2 2 1 Hydrogen Oxygen

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

20. Chemical Formulas cont. Writing chemical formulas: Follow right to left pattern on the Periodic Table of Elements Ex. NaCl sodium is a metal located on the far left and Cl is located farther to the right Therefore, the formula is written as NaCl instead of ClNa

21. If a molecule is made out of one type of atom, it is called A. Element

22. If a molecule is made out of different types of atoms it is? B. Compound

23. Chemical Equations Chemical equation tells about a chemical reaction. It shows the substances we start with. It shows the new substances that are formed.