1. Combination of Atoms

2. 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.

3. 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 Element Chemical Symbol OxygenO NitrogenN HydrogenH SodiumNa

4. 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 H 2 O: 2 atoms of hydrogen, 1 atom of oxygen Ex. 2: Iron Oxide molecule Fe 2 O 3 : 2 atoms of iron, 3 atom of oxygen

5. Chemical Formulas - Examples  Calcium Carbonate (chalk) – CaCO 3  Sodium Chloride (salt) – NaCl  Acetysalicylic acid (aspirin) – C 9 H 4 O 8  Acetic acid (vinegar) – C 2 H 4 O 2 

6. Chemical Formulas  NOTES: - Each symbol in a formula represents an element. - 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 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. - 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.

9. (c) McGraw Hill Ryerson 2007  Chemical reactions result in chemical changes. Chemical changes occur when new substances are created.Chemical changes occur when new substances are created. The original substance(s), called reactants, change into new substance(s) called products.The original substance(s), called reactants, change into new substance(s) called products. See pages 202 - 203

10. (c) McGraw Hill Ryerson 2007 See pages 202 - 203

11. Ionic & Covalent bonding

12. Bond Formation The positive sodium ion and the negative chloride ion are strongly attracted to each other. How Elements Bond 2 2 This attraction, which holds the ions close together, is a type of chemical bond called an ionic bond.

13. Bond Formation The compound sodium chloride, or table salt, is formed. How Elements Bond 2 2 A compound is a pure substance containing two or more elements that are chemically bonded.

14. More Gains and Losses Can elements lose or gain more than one electron? How Elements Bond 2 2 The element magnesium, Mg, in Group 2 has two electrons in its outer energy level. Magnesium can lose these two electrons and achieve a completed energy level.

15. More Gains and Losses Some atoms, such as oxygen, need to gain two electrons to achieve stability. How Elements Bond 2 2 The two electrons released by one magnesium atom could be gained by a single atom of oxygen. When this happens, magnesium oxide (MgO) is formed.

16. Convalent Bonds—Sharing Some atoms are unlikely to lose or gain electrons because the number of electrons in their outer levels makes this difficult. How Elements Bond 2 2 The alternative is sharing electrons.

17. The Convalent Bond The chemical bond that forms between nonmetal atoms when they share electrons is called a covalent bond. How Elements Bond 2 2 Click image to view movie.

18. The Convalent Bond Shared electrons are attracted to the nuclei of both atoms. How Elements Bond 2 2 They move back and forth between the outer energy levels of each atom in the covalent bond. So, each atom has a stable outer energy level some of the time.

19. The Convalent Bond The neutral particle is formed when atoms share electrons is called a molecule How Elements Bond 2 2

20. The Convalent Bond How Elements Bond 2 2 A molecule is the basic unit of a molecular compound.

21. The Convalent Bond How Elements Bond 2 2 You can see how molecules form by sharing electrons in this figure.

22. Mixtures

23. What Is A Mixture?  A mixture is the physical combination of 2 or more substances  It is important to understand that a mixture is not chemically combined  Mixtures can be separated by physical means such as filtration, distillation, and chromatography  Mixtures can be divided into 2 groups Homogenous mixturesHomogenous mixtures Heterogeneous mixturesHeterogeneous mixtures

24. How Do Mixtures Form?  Mixtures form by physically “junking” 2 or more substances together  Remember no chemical change is occurring  The formation of a mixture is not a result of lowering energy

25. What Is a Homogenous Mixture?  A homogeneous mixture is a mixture that is evenly distributed  Homogeneous mixtures are commonly called solutions. Solution = Solute + SolventSolution = Solute + Solvent  Solute: “stuff” being dissolved  Solvent: “stuff” doing the dissolving  The solvent is present in greater quantity  The solute is present in the lesser quantity Ex: Salt water: Salt=solute, Water=solventEx: Salt water: Salt=solute, Water=solvent

26. What Is a Heterogeneous Mixture?  A heterogeneous mixture is a mixture that is unevenly distributed.  Examples: Iced tea: The ice is floating at the top and therefore is not evenly distributed throughout the teaIced tea: The ice is floating at the top and therefore is not evenly distributed throughout the tea Chex Mix: You may find a different number of pretzels or Chex cereal in each handful; therefore, the mixture is unevenly distributedChex Mix: You may find a different number of pretzels or Chex cereal in each handful; therefore, the mixture is unevenly distributed

27. How Are Mixtures Important To My Life?  We encounter mixtures everywhere in our lives  Where would you be without: Ice creamIce cream Kool-aidKool-aid ShampooShampoo SoupSoup MilkMilk Orange juiceOrange juice