1. Chemical Bonds Chapter 11 Review Physical Science Mrs. Nell

2. Why Atoms Combine Compounds – When 2 or more elements chemically combine – Properties are unlike those of their elements Elements form compounds – Chemically stable if outer energy level is completely filled with electrons (like noble gases) – Atoms will gain, lose, or share electrons with other atoms in an effort to become chemically stable (form chemical bonds)

3. Ionic Bonds Ions are atoms that have either gained or lost electrons, giving them either a positive or a negative charge. Compounds made up of ions are ionic compounds. The bonds that hold them together are ionic bonds. Ionic compounds are solids at room temperature and have high melting points. Ionic bonds occur between metals and nonmetals.

4. Covalent Bonds Most atoms become chemically stable by sharing electrons. This is called a covalent bond. Neutral particles formed from shared electrons are called molecules. Covalent bonds form liquids or gases at room temperature. These bonds form between nonmetals and nonmetals.

5. Why Won’t You Share?! Molecules don’t always share electrons equally. Polar molecules have a slightly positive end and a slightly negative end. Nonpolar molecules share their electrons equally.

6. Ionic or Covalent? 1. F 2 2. CaCl 2 3. Na 2 SO 4 4. NH 3 Covalent Ionic Metal + Polyatomic ion (ionic) Covalent

7. Chemical Risks in the Home Hazardous chemicals effect the health and safety of people and/or harms the environment. Hazardous chemicals can be toxic, corrosive, or flammable.

8. Toxic There are many toxic, or poisonous, chemicals found in the home. Some examples are: – disinfectants – Insect repellent – Antifreeze – Ammonia (reacts with bleach) – Mothballs – Motor oils – Rat poison – Windshield wiper fluid – Weed killers

9. Corrosive Corrosive compounds can damage human skin or can eat away at certain metals. Some examples are: – Batteries – Bleach – Drain Cleaners – Oven Cleaners

10. Flammable Flammable compounds burn easily. Some examples: – Gasoline – Paint Thinners – Aerosols

11. Type of Bonding The type of bonding in a compound helps determine how hazardous it is. Compounds formed by covalent bonds evaporate easily. They can be easily inhaled and are flammable. Compounds formed by ionic bonds are less likely to evaporate.

12. Preventing Pollution To prevent pollution from hazardous materials we can: – Use safer alternatives – Recycle oil, antifreeze, and batteries – Buy only the amount you need – Store them in their original containers – Keep hazardous materials that evaporate easily in their original containers

13. Oxidation Numbers Oxidation numbers show how many electrons an atom has gained, lost, or shared when bonding with other atoms. We can use oxidation numbers to figure out chemical formulas.

14. Writing Chemical Formulas To write formulas for binary compounds: 1.Write the symbol of the element with the positive oxidation number 2.Write the symbol of the element with the negative oxidation number 3.Add subscripts so the sum of the oxidation numbers of all atoms in the formula is zero.

15. 4 Practice Problems 1. Potassium bromide 2.Calcium oxide 3.Copper (I) iodide 4.Aluminum sulfide KBr CaO CuI Al 2 S 3

16. Naming Binary Compounds 1.Write the name of the first element 2.Write the root of the name of the second element 3.Add the ending –ide to the root

17. Variable Oxidation Numbers *If the first element has variable oxidation numbers, you must include the oxidation number of the element in parentheses.

18. 4 Practice Problems Write the name of the following binary compounds: 1.NiS 2.FeO 3.FeCl 3 4.Al 2 S 3 Nickel (II) sulfide Iron (II) oxide Iron (III) chloride Aluminum sulfide

19. Polyatomic Ions To name compounds with polyatomic ions: 1.Write the name of the (+) element 2.Find the name of the polyatomic ion ChargeNameFormula 1+AmmoniumNH 4 + 1-AcetateC2H3O2-C2H3O2- 1-ChlorateClO 3 1-HydroxideOH - 1-NitrateNO 3 - 2-CarbonateCO 3 - 2-SulfateSO 4 2- 3-PhosphatePO 4 3-

20. Practice Problems 1.Ca(NO 3 ) 2 2.KNO 3 3.Ba(OH) 2 4.Li 2 CO 3 5.Al 2 (SO 4 ) 3 6.NH 4 ClO 3 Calcium nitrate Potassium nitrate Barium hydroxide Lithium carbonate Aluminum sulfate Ammonium chlorate

21. Formulas with Polyatomic Ions 1.Follow rules for binary compounds 2.Write parentheses around the group representing the polyatomic ion when more than one of that ion is needed

22. Practice Problems 1.Sodium nitrate 2.Potassium acetate 3.Aluminum sulfate 4.Lithium chlorate 5.Magnesium nitrate 6.Ammonium acetate 7.Silver nitrate NaNO 3 KC 2 H 3 O 2 Al 2 (SO 4 ) 3 LiClO 3 Mg(NO 3 ) 2 NH 4 C 2 H 3 O 2 AgNO 3

23. Hydrates Some ionic compounds have water molecules chemically attached to their ions. These compounds are called hydrates. You can remove water from these crystals by heating them. Hydrates are used in skin-care products like shampoo or lotion for moisture.

24. Anhydrous An anhydrous compound does not have water molecules as part of their structure. Anhydrates help remove water to maintain dryness in paper products. Silica gel packs are placed in many store items to absorb large amounts of water and prevent damage to the product.