1. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu How to Use This Presentation To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show.” To advance through the presentation, click the right-arrow key or the space bar. From the resources slide, click on any resource to see a presentation for that resource. From the Chapter menu screen click on any lesson to go directly to that lesson’s presentation. You may exit the slide show at any time by pressing the Esc key.

2. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Chapter Presentation Transparencies Bellringer Standardized Test PrepVisual Concepts Sample Problems Resources

3. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Table of Contents Chapter 6 Covalent Compounds Section 1 Covalent Bonds Section 2 Drawing and Naming Molecules Section 3 Molecular Shapes

4. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 1 Covalent Bonds Bellringer Make a list of the elements that form ionic bonds. Note that most ionic bonds contain a metal and a nonmetal. Chapter 6

5. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives Explain the role and location of electrons in a covalent bond. Describe the change in energy and stability that takes place as a covalent bond forms. Distinguish between nonpolar and polar covalent bonds based on electronegativity differences. Section 1 Covalent Bonds Chapter 6

6. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives, continued Compare the physical properties of substances that have different bond types, and relate bond types to electronegativity differences. Section 1 Covalent Bonds Chapter 6

7. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Sharing Electrons When an ionic bond forms, electrons are rearranged and are transferred from one atom to another to form charged ions. In another kind of change involving electrons, the neutral atoms share electrons. Section 1 Covalent Bonds Chapter 6

8. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Sharing Electrons, continued Forming Molecular Orbitals A covalent bond is a bond formed when atoms share one or more pairs of electrons. The shared electrons move within a space called a molecular orbital. A molecular orbital is the region of high probability that is occupied by an individual electron as it travels with a wavelike motion in the three-dimensional space around one of two or more associated nuclei. Section 1 Covalent Bonds Chapter 6

9. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Formation of a Covalent Bond Chapter 6

10. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Chemical Bond Chapter 6

11. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Stability Energy Is Released When Atoms Form a Covalent Bond Section 1 Covalent Bonds Chapter 6

12. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Stability, continued Potential Energy Determines Bond Length When two bonded hydrogen atoms are at their lowest potential energy, the distance between them is 75 pm. The bond length is the distance between two bonded atoms at their minimum potential energy. However, the two nuclei in a covalent bond vibrate back and forth. The bond length is thus the average distance between the two nuclei. Section 1 Covalent Bonds Chapter 6

13. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Bond Length Chapter 6

14. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Energy and Stability, continued Bonded Atoms Vibrate, and Bonds Vary in Strength The bond length is the average distance between two nuclei in a covalent bond. At a bond length of 75 pm, the potential energy of H 2 is –436 kJ/mol. Thus 436 kJ of energy must be supplied to break the bonds in 1 mol of H 2 molecules. The energy required to break a bond between two atoms is the bond energy. Bonds that have the higher bond energies (stronger bonds) have the shorter bond lengths. Section 1 Covalent Bonds Chapter 6

15. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Bond Energy Chapter 6

16. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Covalent Bonding In covalent bonds between two different atoms, the atoms often have different attractions for shared electrons. Electronegativity values are a useful tool to predict what kind of bond will form. Section 1 Covalent Bonds Chapter 6

17. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Electronegativity Chapter 6

18. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Covalent Bonding, continued Atoms Share Electrons Equally or Unequally Section 1 Covalent Bonds When the electronegativity values of two bonding atoms are similar, bonding electrons are shared equally. A covalent bond in which the bonding electrons in the molecular orbital are shared equally is a nonpolar covalent bond. Chapter 6

19. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Covalent Bonding, continued Atoms Share Electrons Equally or Unequally, continued Section 1 Covalent Bonds When the electronegativity values of two bonding atoms are different, bonding electrons are shared unequally. A covalent bond in which the bonding electrons in the molecular orbital are shared unequally is a polar covalent bond. Chapter 6

20. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Predicting Bond Character from Electronegativity Differences Chapter 6

21. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Covalent Bonding, continued Polar Molecules Have Positive and Negative Ends Section 1 Covalent Bonds In a polar covalent bond, the ends of the bond have opposite partial charges. A molecule in which one end has a partial positive charge and the other end has a partial negative charge is called a dipole. In a polar covalent bond, the shared pair of electrons is not transferred completely. Instead, it is more likely to be found near the more electronegative atom. Chapter 6

22. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Covalent Bonding, continued Polar Molecules Have Positive and Negative Ends, continued Section 1 Covalent Bonds The symbol  is used to mean partial.  + is used to show a partial positive charge  – is used to show a partial negative charge charge example: H  + F  – Because the F atom has a partial negative charge, the electron pair is more likely to be found nearer to the fluorine atom Chapter 6

23. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Comparing Polar and Nonpolar Covalent Bonds Chapter 6

24. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Polarity Is Related to Bond Strength In general, the greater the electronegativity difference, the greater the polarity and the stronger the bond. Section 1 Covalent Bonds Chapter 6

25. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Electronegativity and Bond Types Section 1 Covalent Bonds Differences in electronegativity values provide one model that can tell you which type of bond two atoms will form. Another general rule states: A covalent bond forms between two nonmetals. An ionic bond forms between a nonmetal and a metal. Chapter 6

26. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Properties of Substances Depend on Bond Type Section 1 Covalent Bonds The type of bond that forms (metallic, ionic, or covalent) determines the properties of the substance. The difference in the strength of attraction between the basic units of ionic and covalent substances causes these types of substances to have different properties. Chapter 6

27. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Properties of Substances with Metallic, Ionic, and Covalent Bonds Chapter 6

28. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 2 Drawing and Naming Molecules Bellringer Classify the following compounds according to the type of bonds they contain: NO CO HF NaCl HBr NaI Chapter 6

29. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives Draw Lewis structures to show the arrangement of valence electrons among atoms in molecules and polyatomic ions. Explain the differences between single, double, and triple covalent bonds. Draw resonance structures for simple molecules and polyatomic ions, and recognize when they are required. Section 2 Drawing and Naming Molecules Chapter 6

30. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives, continued Name binary inorganic covalent compounds by using prefixes, roots, and suffixes. Section 2 Drawing and Naming Molecules Chapter 6

31. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures Valence electrons are the electrons in the outermost energy level of an atom. A Lewis structure is a structural formula in which valence electrons are represented by dots. In Lewis structures, dot pairs or dashes between two atomic symbols represent pairs in covalent bonds. Section 2 Drawing and Naming Molecules Chapter 6

32. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Valence Electrons Chapter 6

33. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures, continued Lewis Structures Show Valence Electrons As you go from element to element across a period, you add a dot to each side of the element’s symbol. Section 2 Drawing and Naming Molecules Chapter 6

34. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures, continued Lewis Structures Show Valence Electrons, continued Section 2 Drawing and Naming Molecules You do not begin to pair dots until all four sides of the element’s symbol have a dot. Chapter 6

35. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures, continued Lewis Structures Show Valence Electrons, continued An element with an octet of valence electrons has a stable configuration. The tendency of bonded atoms to have octets of valence electrons is called the octet rule. Section 2 Drawing and Naming Molecules Chapter 6

36. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts The Octet Rule Chapter 6

37. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures, continued Lewis Structures Show Valence Electrons, continued When two chlorine atoms form a covalent bond, each atom contributes one electron to a shared pair. Section 2 Drawing and Naming Molecules Chapter 6 An unshared pair, or a lone pair, is a nonbonding pair of electrons in the valence shell of an atom.

38. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Lewis Electron-Dot Structures, continued Lewis Structures Show Valence Electrons, continued A single bond is a covalent bond in which two atoms share one pair of electrons The electrons can pair in any order. However, any unpaired electrons are usually filled in to show how they will form a covalent bond. Section 2 Drawing and Naming Molecules Chapter 6

39. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Single Bonds Sample Problem A Draw a Lewis structure for CH 3 I. Section 2 Drawing and Naming Molecules Chapter 6

40. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Single Bonds Sample Problem A Solution Draw each atom’s Lewis structure, and count the total number of valence electrons. Section 2 Drawing and Naming Molecules Chapter 6 number of dots: 14 Arrange the Lewis structure so that carbon is the central atom.

41. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Single Bonds Sample Problem A Solution, continued Distribute one bonding pair of electrons between each of the bonded atoms. Then, distribute the remaining electrons, in pairs, around the remaining atoms to form an octet for each atom. Section 2 Drawing and Naming Molecules Chapter 6 Change each pair of dots that represents a shared pair of electrons to a long dash.

42. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures for Polyatomic Ions Sample Problem B Draw a Lewis structure for the sulfate ion, Section 2 Drawing and Naming Molecules Chapter 6

43. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures for Polyatomic Ions Sample Problem B Solution Count electrons for all atoms. Add two additional electrons to account for the 2− charge on the ion. Section 2 Drawing and Naming Molecules Chapter 6 number of dots: 30 + 2 = 32 Distribute the 32 dots so that there are 8 dots around each atom.

44. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures for Polyatomic Ions Sample Problem B Solution, continued Change each bonding pair to a long dash. Place brackets around the ion and a 2  charge outside the bracket to show that the charge is spread out over the entire ion. Section 2 Drawing and Naming Molecules Chapter 6

45. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Bonds For O 2 to make an octet, each atom needs two more electrons. The two atoms share four electrons. Section 2 Drawing and Naming Molecules Chapter 6 A double bond is a covalent bond in which two atoms share two pairs of electrons.

46. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Bonds, continued For N 2 to make an octet, each atom needs three more electrons. The two atoms share six electrons. Section 2 Drawing and Naming Molecules Chapter 6 A triple bond is a covalent bond in which two atoms share three pairs of electrons.

47. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Comparing Single, Double, and Triple Bonds Chapter 6

48. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Multiple Bonds Sample Problem C Draw a Lewis structure for formaldehyde, CH 2 O. Section 2 Drawing and Naming Molecules Chapter 6

49. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Multiple Bonds Sample Problem C Solution Draw each atom’s Lewis structure, and count the total dots. Section 2 Drawing and Naming Molecules Chapter 6 number of dots: 12 Arrange the atoms so that carbon is the central atom. O HC H

50. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Drawing Lewis Structures with Multiple Bonds Sample Problem C Solution, continued Distribute one pair of dots between each of the atoms and the rest, in pairs, around the atoms. C does not have an octet. To get an octet, move an unshared pair from the O to between the O and the C. Section 2 Drawing and Naming Molecules Chapter 6 Change each bonding pair to a long dash. Two pairs of dots represent a double bond.

51. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Resonance Structures Some molecules, such as ozone, O 3, cannot be represented by a single Lewis structure. When a molecule has two or more possible Lewis structures, the two structures are called resonance structures. Section 2 Drawing and Naming Molecules Chapter 6

52. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Atomic Resonance Chapter 6

53. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Multiple Bonds, continued Naming Covalent Compounds The first element named is usually the first one written in the formula. It is usually the less-electronegative element. The second element named has the ending -ide. Unlike the names for ionic compounds, the names for covalent compounds must often distinguish between two different molecules made of the same elements. Section 2 Drawing and Naming Molecules Chapter 6

54. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Naming Covalent Compounds, continued This system of prefixes is used to show the number of atoms of each element in the molecule. Section 2 Drawing and Naming Molecules Chapter 6

55. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Naming Covalent Compounds, continued Prefixes can be used to show the numbers of each type of atom in diphosphorus pentasulfide. Section 2 Drawing and Naming Molecules Chapter 6

56. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts Naming Compounds Using Numerical Prefixes Chapter 6

57. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Section 3 Molecular Shapes Bellringer Write a short paragraph telling what you think the “valence shell electron pair repulsion theory” might have to do with molecular shape. Chapter 6

58. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Objectives Predict the shape of a molecule using VSEPR theory. Associate the polarity of molecules with the shapes of molecules, and relate the polarity and shape of molecules to the properties of a substance. Section 3 Molecular Shapes Chapter 6

59. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Determining Molecular Shapes The three-dimensional shape of a molecule is important in determining the molecule’s physical and chemical properties. Section 3 Molecular Shapes A Lewis Structure Can Help Predict Molecular Shape You can predict the shape of a molecule by examining the Lewis structure of the molecule. Chapter 6

60. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Determining Molecular Shapes, continued A Lewis Structure Can Help Predict Molecular Shape, continued The valence shell electron pair repulsion (VSEPR) theory is a theory that predicts some molecular shapes based on the idea that pairs of valence electrons surrounding an atom repel each other. Section 3 Molecular Shapes Chapter 6

61. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Determining Molecular Shapes, continued Electron Pairs Can Determine Molecular Shape According to the VSEPR theory, the shape of a molecule is determined by the valence electrons surrounding the central atom. Electron pairs are negative, so they repel each other. Therefore, the shared pairs that form different bonds repel each other and remain as far apart as possible. Section 3 Molecular Shapes Chapter 6

62. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Determining Molecular Shapes, continued Electron Pairs Can Determine Molecular Shape, continued For CO 2, the two double bonds around the central carbon atom repel each other and remain far apart. Section 3 Molecular Shapes Chapter 6 For BF 3, the three single bonds around the central fluorine atom will be at a maximum distance apart.

63. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Determining Molecular Shapes, continued Electron Pairs Can Determine Molecular Shape, continued The four shared pairs of electrons in CH 4 are farthest apart when each pair is positioned at the corners of a tetrahedron. Section 3 Molecular Shapes Chapter 6

64. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts VSEPR and Lone Electron Pairs Chapter 6

65. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Visual Concepts VSEPR and Basic Molecular Shapes Chapter 6

66. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Predicting Molecular Shapes Sample Problem D Determine the shape of H 2 O. Section 3 Molecular Shapes Chapter 6

67. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Predicting Molecular Shapes Sample Problem D Solution Draw the Lewis structure for H 2 O. Section 3 Molecular Shapes Chapter 6 Count the number of shared and unshared pairs of electrons around the central atom. H 2 O has two shared pairs and two unshared pairs.

68. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Predicting Molecular Shapes Sample Problem D Solution, continued Find the shape that allows the shared and unshared pairs of electrons to be as far apart as possible. The water molecule will have a bent shape. Section 3 Molecular Shapes Chapter 6

69. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Molecular Shape Affects a Substance’s Properties Shape Affects Polarity Section 3 Molecular Shapes One property that shape determines is the polarity of a molecule. The polarity of a molecule that has more than two atoms depends on the polarity of each bond and the way the bonds are arranged in space. Chapter 6

70. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Molecular Shape Affects a Substance’s Properties, continued Shape Affects Polarity, continued Section 3 Molecular Shapes If two dipoles are arranged in opposite directions, they will cancel each other. If two dipoles are arranged at an angle, they will not cancel each other. Compare the molecules of nonpolar carbon dioxide, CO 2, which has a linear shape, and polar water, H 2 O, which has a bent shape. Chapter 6

71. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Molecular Shape Affects Polarity Chapter 6

72. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 1. Which of these combinations is likely to have a polar covalent bond? A.two atoms of similar size B.two atoms of very different size C.two atoms with different electronegativities D.two atoms with the same number of electrons Standardized Test Preparation Understanding Concepts Chapter 6

73. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 1. Which of these combinations is likely to have a polar covalent bond? A.two atoms of similar size B.two atoms of very different size C.two atoms with different electronegativities D.two atoms with the same number of electrons Understanding Concepts Standardized Test Preparation Chapter 6

74. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. According to VSEPR theory, which of these is caused by repulsion between electron pairs surrounding an atom? F.breaking of a chemical bond G.formation of a sea of electrons H.formation of a covalent chemical bond I.separation of electron pairs as much as possible Understanding Concepts Chapter 6 Standardized Test Preparation

75. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 2. According to VSEPR theory, which of these is caused by repulsion between electron pairs surrounding an atom? F.breaking of a chemical bond G.formation of a sea of electrons H.formation of a covalent chemical bond I.separation of electron pairs as much as possible Understanding Concepts Chapter 6 Standardized Test Preparation

76. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3.How many electrons are shared in a double covalent bond? A.2 B.4 C.6 D.8 Understanding Concepts Chapter 6 Standardized Test Preparation

77. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 3.How many electrons are shared in a double covalent bond? A.2 B.4 C.6 D.8 Understanding Concepts Chapter 6 Standardized Test Preparation

78. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 4.How can the difference in number of valence electrons between nitrogen and carbon account for the fact that the boiling point of ammonia, NH 3, is 130°C higher than that of methane, CH 4. Understanding Concepts Chapter 6 Standardized Test Preparation

79. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 4.How can the difference in number of valence electrons between nitrogen and carbon account for the fact that the boiling point of ammonia, NH 3, is 130°C higher than that of methane, CH 4. Answer: Ammonia is a polar molecule because nitrogen has a pair of electrons that are not involved in a covalent bond, while methane is a nonpolar molecule. The attraction between polar ammonia molecules causes the higher boiling point. Understanding Concepts Chapter 6 Standardized Test Preparation

80. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 5.Why don’t scientists need VESPR theory to predict the shape of HCl? Understanding Concepts Chapter 6 Standardized Test Preparation

81. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 5.Why don’t scientists need VESPR theory to predict the shape of HCl? Answer: Because HCl has two atoms, the shape can be only linear. Understanding Concepts Chapter 6 Standardized Test Preparation

82. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 6.What are the attractive and repulsive forces involved in a covalent bond and how do their total strengths compare? Understanding Concepts Chapter 6 Standardized Test Preparation

83. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 6.What are the attractive and repulsive forces involved in a covalent bond and how do their total strengths compare? Answer: Attractive forces exist between each electron and each nucleus. Repulsive forces exist between electrons and between nuclei. In a covalent bond, total attractive and repulsive forces are balanced. Understanding Concepts Chapter 6 Standardized Test Preparation

84. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Read the passage below. Then answer the questions. Although water is a polar molecule, pure water does not carry an electric current. It is a good solvent for many ionic compounds, and solutions of ionic compounds in water do carry electric currents. The charged particles in solution move freely, carrying electric charges. Even a dilute solution of ions in water becomes a good conductor. Without ions in solution, there is very little electrical conductivity. Reading Skills Chapter 6 Standardized Test Preparation

85. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 7.Why is a solution of sugar in water not a good electrical conductor? F.Sugar does not form ions in solution. G.The ionic bonds of sugar molecules are too strong to carry a current. H. Not enough sugar dissolves for the solution to become a conductor. I. A solution of sugar in water is not very conductive because it is mostly water, which is not very conductive. Reading Skills Chapter 6 Standardized Test Preparation

86. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reading Skills Chapter 6 Standardized Test Preparation 7.Why is a solution of sugar in water not a good electrical conductor? F.Sugar does not form ions in solution. G.The ionic bonds of sugar molecules are too strong to carry a current. H. Not enough sugar dissolves for the solution to become a conductor. I. A solution of sugar in water is not very conductive because it is mostly water, which is not very conductive.

87. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Reading Skills Chapter 6 Standardized Test Preparation 8.Why do molten ionic compounds generally conduct electric current well, while molten covalent compounds generally do not? A.Ionic compounds are more soluble in water. B.Ionic compounds have more electrons than compounds. C.When they melt, ionic compounds separate into charged particles. D.Most ionic compounds contain a metal atom which carries the electric current.

88. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 8.Why do molten ionic compounds generally conduct electric current well, while molten covalent compounds generally do not? A.Ionic compounds are more soluble in water. B.Ionic compounds have more electrons than compounds. C.When they melt, ionic compounds separate into charged particles. D.Most ionic compounds contain a metal atom which carries the electric current. Reading Skills Chapter 6 Standardized Test Preparation

89. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9.If water is not a good conductor of electric current, why is it dangerous to handle an electrical appliance when your hands are wet or when you are standing on wet ground? Reading Skills Chapter 6 Standardized Test Preparation

90. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 9.If water is not a good conductor of electric current, why is it dangerous to handle an electrical appliance when your hands are wet or when you are standing on wet ground? Answer: Because even a small amount of ionic compounds dissolved in water makes it a good conductor. The salts in your body or on the ground are enough to cause the water to carry a current. Reading Skills Chapter 6 Standardized Test Preparation

91. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu Use the diagram below to answer question 10. Interpreting Graphics Chapter 6 Standardized Test Preparation

92. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 10. The diagram above best represents which type of chemical bond? F.ionic G.metallic H.nonpolar covalent I.polar covalent Interpreting Graphics Chapter 6 Standardized Test Preparation

93. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 10. The diagram above best represents which type of chemical bond? F.ionic G.metallic H.nonpolar covalent I.polar covalent Interpreting Graphics Chapter 6 Standardized Test Preparation

94. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu The table below shows the connection between electronegativity and bond strength (kilojoules per mole). Use it to answer questions 11 through 13. Interpreting Graphics Chapter 6 Standardized Test Preparation

95. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 11.Which of these molecules has the smallest partial positive charge on the hydrogen end of the molecule? A.HF B.HCl C.HBr D.HI Interpreting Graphics Chapter 6 Standardized Test Preparation

96. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 11.Which of these molecules has the smallest partial positive charge on the hydrogen end of the molecule? A.HF B.HCl C.HBr D.HI Interpreting Graphics Chapter 6 Standardized Test Preparation

97. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 12.How does the polarity of the bond between a halogen and hydrogen relate to the number of electrons of the halogen atom? F.Polarity is not related to the number of electrons of the halogen atom. G.Polarity decreases as the number of unpaired halogen electrons increases. H.Polarity decreases as the total number of halogen atom electrons increases. I.Polarity decreases as the number of valence electrons of the halogen atom increases. Interpreting Graphics Chapter 6 Standardized Test Preparation

98. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 12.How does the polarity of the bond between a halogen and hydrogen relate to the number of electrons of the halogen atom? F.Polarity is not related to the number of electrons of the halogen atom. G.Polarity decreases as the number of unpaired halogen electrons increases. H.Polarity decreases as the total number of halogen atom electrons increases. I.Polarity decreases as the number of valence electrons of the halogen atom increases. Interpreting Graphics Chapter 6 Standardized Test Preparation

99. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 13.Based on the information in this table, how does the electronegativity difference in a covalent bond relate to the strength of the bond? Interpreting Graphics Chapter 6 Standardized Test Preparation

100. Copyright © by Holt, Rinehart and Winston. All rights reserved. ResourcesChapter menu 13.Based on the information in this table, how does the electronegativity difference in a covalent bond relate to the strength of the bond? Answer: A stronger bond is indicated by greater bond energy, so the strength of the bond increases as electronegativity increases. Interpreting Graphics Chapter 6 Standardized Test Preparation