2. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules Objectives Distinguish between compounds and mixtures. Relate the chemical formula of a compound to the relative numbers of atoms or ions present in the compound. Use models to visualize a compound’s chemical structure. Describe how the chemical structure of a compound affects its properties. Chapter 5

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules What Are Compounds? Chemical bonds distinguish compounds from mixtures. A compound is held together by chemical bonds. A chemical bond is the attractive force that holds atoms or ions together. A compound always has the same chemical formula. Chapter 5

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. Compounds Section 1 Compounds and Molecules Chapter 5

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chemical Bond Section 1 Compounds and Molecules Chapter 5

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules What Are Compounds? continued Chemical structure shows the bonding within a compound. A chemical structure is the arrangement of atoms in a substance. A bond length is the average distance between the nuclei of two bonded atoms. A bond angle is the angle formed by two bonds to the same atom. Chapter 5

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. Bond Length Section 1 Compounds and Molecules Chapter 5

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. Bond Angle Section 1 Compounds and Molecules Chapter 5

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules Models of Compounds Some models give you an idea of bond lengths and angles. The ball-and-stick model of water shown at right represents bond lengths and bond angles. Chapter 5 In structural formulas, only chemical symbols are used to represent the atoms. Space-filling models show the space occupied by atoms.

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules How Does Structure Affect Properties? Compounds with network structures are strong solids. Example: Quartz is made of silicon and oxygen atoms bonded in a strong, rigid structure: Chapter 5

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules How Does Structure Affect Properties? continued Compounds made of networks of bonded ions have high melting points and boiling points. Example: Table salt—sodium chloride—is made of a tightly packed repeating network of positive sodium ions and negative chlorine ions. Chapter 5

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 Compounds and Molecules How Does Structure Affect Properties? continued Some compounds are made of molecules. Some compounds made of molecules are solids, others are liquids, others are gases. The strength of attractions between molecules varies. Attractions between water molecules are called hydrogen bonds. Hydrogen bonding is depicted on the next slide. Chapter 5

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. Water Bonding Section 1 Compounds and Molecules Chapter 5

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Objectives Explain why atoms sometimes join to form bonds. Explain why some atoms transfer their valence electrons to form ionic bonds, while other atoms share valence electrons to form different bonds. Differentiate between ionic, covalent, and metallic bonds. Compare the properties of substances with different types of bonds. Chapter 5

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding What Holds Bonded Atoms Together? Bonded atoms usually have a stable electron configuration. Example: As shown at right, when two hydrogen atoms bond, their electron clouds overlap. The resulting hydrogen molecule has an electronic structure similar to the noble gas helium. Chapter 5

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding What Holds Bonded Atoms Together? continued Bonds can bend and stretch without breaking. Although a “bar” is sometimes used to represent a bond between two atoms, chemical bonds behave more like flexible springs. Chapter 5

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Ionic Bonds Ionic bonds are formed between oppositely charged ions. As shown at right, ionic compounds are in the form of networks of formula units, not molecules. Chapter 5 When melted or dissolved in water, ionic compounds conduct electricity.

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. Ionic Bonding Section 2 Ionic and Covalent Bonding Chapter 5

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Metallic Bonds A metallic bond is a bond formed by the attraction between positively charged metal ions and the electrons around them. Electrons move freely between metal atoms. This model explains why metals: conduct electricity conduct heat are flexible Chapter 5

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. Metallic Bonding Section 2 Ionic and Covalent Bonding Chapter 5

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Covalent Bonds A covalent bond is a bond formed when atoms share one or more pairs of electrons. Covalent compounds can be solids, liquids, or gases. Bonds in which atoms share electrons equally are called nonpolar covalent bonds, as shown below. Chapter 5

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Covalent Bonds, continued Atoms do not always share electrons equally. An unequal sharing of electrons forms a polar covalent bond. Atoms may share more than one pair of electrons. Chapter 5

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. Comparing Polar and Nonpolar Covalent Bonds Section 2 Ionic and Covalent Bonding Chapter 5

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Polyatomic Ions A polyatomic ion is an ion made of two or more atoms. There are many common polyatomic ions. Some are shown at right. See page 158 Chapter 5 Parentheses group the atoms of a polyatomic ion. Example: the chemical formula for ammonium sulfate is written as (NH 4 ) 2 SO 4, not N 2 H 8 SO 4.

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Ionic and Covalent Bonding Polyatomic Ions, continued Some polyatomic anion names relate to their oxygen content. An -ate ending is used to name an ion with more oxygen. Examples: sulfate (SO 4 2– ), nitrate (NO 3 – ), chlorate (ClO 3 – ) An -ite ending is used to name an ion with less oxygen. Examples: sulfite (SO 3 2– ), nitrite (NO 2 – ), chlorite (ClO 2 – ) Chapter 5

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. Comparing Ionic and Molecular Compounds Section 2 Ionic and Covalent Bonding Chapter 5

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Objectives Name simple ionic and covalent compounds. Predict the charge of a transition metal cation in an ionic compound. Write chemical formulas for simple ionic compounds. Distinguish a covalent compound’s empirical formula from its molecular formula. Chapter 5

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. Reading Chemical Formulas Section 3 Compound Names and Formulas Chapter 5

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Naming Ionic Compounds Names of cations include the elements of which they are composed. Example: when an atom of sodium loses an electron, a sodium ion, Na +, forms. Names of anions are altered names of elements. Example: when an atom of fluorine gains an electron, a fluoride ion, F –, forms. Chapter 5

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Naming Ionic Compounds Some cation names must show their charge. Iron can form two different cations. Fe 2 O 3 is made of Fe 3+ ions, so it is named iron(III)oxide. FeO is made of Fe 2+ ions, so it is named iron(II) oxide. To determine the charge of a transition metal cation, look at the total charge of the compound. You can tell that the iron ion in Fe 2 O 3 has a charge of 3+ because the total charge of the compound must be zero, and an oxide ion, O 2–, has a a charge of 2–. Fe 2 O 3 → (2 × 3+) + (3 × 2–) = 0 Chapter 5

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. Naming Ionic Compounds Section 3 Compound Names and Formulas Chapter 5

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Math Skills Writing Ionic Formulas What is the chemical formula for aluminum fluoride? 1. List the symbols for each ion. Symbol for an aluminum ion (from Table 4 in your book): Al 3+ Symbol for a fluoride ion from (from Table 5 in your book): F – 2. Write the symbols for the ions with the cation first. Al 3+ F – Chapter 5

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. Math Skills, continued 3. Find the least common multiple of the ions’ charges. The least common multiple of 3 and 1 is 3. To make a neutral compound, you need a total of three positive charges and three negative charges. To get three positive charges: you need only one Al 3+ ion because 1 × 3+ = 3+. To get three negative charges: you need three F – ions because 3 × 1– = 3– 4. Write the chemical formula, indicating with subscripts how many of each ion are needed to make a neutral compound. Section 3 Compound Names and Formulas Chapter 5 AlF 3

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Naming Covalent Compounds Numerical prefixes, shown in Table 7 in your book, are used to name covalent compounds of two elements. Examples: There are one boron atom and three fluorine atoms in boron trifluoride, BF 3. Dinitrogen tetroxide, N 2 O 4, is made of two nitrogen atoms and four oxygen atoms. Chapter 5

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. Naming Covalently-Bonded Compounds Section 3 Compound Names and Formulas Chapter 5

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. Naming Compounds Using Numerical Prefixes Section 3 Compound Names and Formulas Chapter 5

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Chemical Formulas for Covalent Compounds A compound’s simplest formula is its empirical formula. An empirical formula tells the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio. Chapter 5

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 3 Compound Names and Formulas Chemical Formulas for Covalent Compounds Different compounds can have the same empirical formula. Molecular formulas are determined from empirical formulas. A molecular formula is a chemical formula that shows the number and kinds of atoms in a molecule. In some cases, a compound’s molecular formula is the same as its empirical formula. Chapter 5

39. Copyright © by Holt, Rinehart and Winston. All rights reserved. Comparing Molecular and Empirical Formulas Section 3 Compound Names and Formulas Chapter 5

40. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Objectives Describe how carbon atoms bond covalently to form organic compounds. Identify the names and structures of groups of simple organic compounds and polymers. Identify what makes up the polymers that are essential to life. Chapter 5

41. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Organic Compounds In chemistry, the word organic is used to describe certain compounds. An organic compound is a covalently bonded compound that contains carbon, excluding carbonates and oxides. Many ingredients of familiar substances contain carbon. Chapter 5

42. Copyright © by Holt, Rinehart and Winston. All rights reserved. Organic Compound Section 4 Organic and Biochemical Compounds Chapter 5

43. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Organic Compounds Carbon atoms form four covalent bonds in organic compounds. When a compound is made of only carbon and hydrogen atoms, it is called a hydrocarbon. Chapter 5

44. Copyright © by Holt, Rinehart and Winston. All rights reserved. Hydrocarbon Section 4 Organic and Biochemical Compounds Chapter 5

45. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Organic Compounds The carbon atoms in any alkane with more than three carbon atoms can have more than one possible arrangement. Carbon atom chains may be branched or unbranched, and they can even form rings. Chapter 5

46. Copyright © by Holt, Rinehart and Winston. All rights reserved. Six-Carbon Alkanes Section 4 Organic and Biochemical Compounds Chapter 5

47. Copyright © by Holt, Rinehart and Winston. All rights reserved. Alcohol Section 4 Organic and Biochemical Compounds Chapter 5

48. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Polymers A polymer is large molecule that is formed by more than five monomers, or small units. Example: polyethene (often known as polyethylene) is a long chain made from many molecules of ethene. Some polymers are natural; others are man-made. Examples: rubber, starch, protein, and DNA are all natural polymers. Plastics and synthetic fibers are man-made polymers. Chapter 5

49. Copyright © by Holt, Rinehart and Winston. All rights reserved. Polymers Section 4 Organic and Biochemical Compounds Chapter 5

50. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Polymers, continued The elasticity of a polymer is determined by its structure. Examples: A milk jug made of polyethene is not elastic: it can be crushed, but does not return to its original shape. A rubber band is an elastic polymer: when it is stretched and released, it returns to its original shape. Chapter 5

51. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Biochemical Compounds A carbohydate is any organic compound that is made of carbon, hydrogen, and oxygen and that provides nutrients to the cells of living things. A protein is an organic compound that is a polymer of amino acids, and a principal component of all cells. An amino acid is any one of 20 different organic molecules that contain a carboxyl and an amino group. Chapter 5

52. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 4 Organic and Biochemical Compounds Biochemical Compounds, continued Your DNA determines your entire genetic makeup. DNA is a polymer with a complex structure. It is in the form of paired strands, in the shape of a twisted ladder known as a double helix. Chapter 5