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206 Chapter 7
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Study Guide
Study Tip
Write and answer questions about the content of the chapter. For Chap- ter 7, you might ask the following questions, which require you to sum- marize the information contained in the chapter. What information does the electron dot structure of an ele- ment provide? (the number of valence electrons around the atom) In most cases, what is the stable electron configuration of an elemental ion? (In most cases, a stable configuration is characterized by an octet of valence elec- trons; the configuration is isoelectronic with that of a noble gas.) Why does NaCl dissolved in water conduct electricity? (In water, the ionic com- pound breaks apart into Na+^ and Cl^ − ions that are free to move in the solu- tion.) What is the theory of bonding in pure metals? (metal cations held together by a pool of mobile valence electrons)
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Chapter Resources
206 Chapter 7
7 Study Guide
Key Concepts 7.1 Ions
- To find the number of valence electrons in an atom of a representative element, simply look at its group number.
- Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level. Atoms of some nonmetallic elements tend to gain elec- trons to achieve a complete octet.
- An atom’s loss of valence electrons produces a positively charged cation.
- The gain of electrons by a neutral atom pro- duces negatively charged anion.
7.2 Ionic Bonds and Ionic Compounds
- Although they are composed of ions, ionic compounds are electrically neutral.
- Most ionic compounds are crystalline solids at room temperature, and they generally have high melting points. Ionic compounds can conduct an electric current when melted or dissolved in water. 7.3 Bonding in Metals
- The valence electrons of metal atoms can be modeled as a sea of electrons.
- Metal atoms are arranged in very compact and orderly patterns.
- Alloys are important because their proper- ties are often superior to those of their com- ponent elements.
- alloys (p. 203)
- chemical formula (p. 195)
- coordination number (p. 198)
- electron dot structure (p. 188)
- formula unit (p. 195)
- halide ion (p. 192)
- ionic bonds (p. 194)
- ionic compounds (p. 194)
- metallic bonds (p. 201)
- octet rule (p. 188)
- valence electron (p. 187)
Vocabulary
Organizing Information Use these terms to construct a concept map that organizes the major ideas of this chapter. (^) ionic bond valence electron
properties of ionic compounds
stable electron configuration
octet rule metallic bond ionic compound
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Ionic and Metallic Bonding 207
CHAPTER
7 Assessment
30. by gaining or losing electrons 31. a. gain of 1 electron b. loss of one electron c. gain of 3 electrons d. loss of 2 electrons e. loss of 1 electron f. gain of 1 electron 32. a. bromide, anion b. sodium, cation c. arsenide, anion d. calcium, cation e. copper, cation f. hydride, anion 33. electrons in the highest occupied energy level 34. a. 7, 5A b. 3, 1A c. 15, 5A d. 56, 2A e. 35, 7A f. 6, 4A 36. a. 2 b. 3 c. 1 d. 2 37. a. Al3+^ b. Li+^ c. Ba2+^ d. K+ e. Ca2+^ f. Sr2+ 38. Most nonmetals gain 1, 2, or 3 elec- trons to achieve a noble-gas elec- tron configuration. 39. a. S^2 −^ b. Na+^ c. F−^ d. P^3 − 40. a. 3 b. 2 c. 1 d. 3 41. a, c, e 42. a. Ca2+, F−^ b. Al3+, Br−^ c. Li+, O^2 − d. Al3+, S^2 −^ e. K+, N^3 − 43. The positive charges balance the negative charges. 44. a, b, d 45. a. K+, Cl−^ b. Ba2+, SO 42 − c. Mg2+, Br−^ d. Li+, CO 32 − 46. Their network of electrostatic attractions and repulsions forms a rigid structure. 47. Ions are free to move in molten MgCl 2. 48. They have many mobile valence electrons. Electrons in the current replace the electrons leaving the metal. 49. body-centered cubic: Na, K, Fe, Cr, or W; face-centered cubic: Cu, Ag, Au, Al, or Pb; hexagonal close- packed: Mg, Zn, or Cd 35. a. Cl b. S c. Al d. Li 50. Answers will vary and could include table- ware, steel in cars and buses, high-speed dental drill bits, solder in stereos and televi- sions, and structural steel in buildings. 51. The properties of the steel will vary accord- ing to its composition. In addition to iron, steel can contain varying amounts of car- bon and such metals as chromium, nickel, and molybdenum.
7 Assessment
Reviewing Content
Assessment 207
7.1 Ions
- Describe two ways that an ion forms from an atom.
- State the number of electrons either lost or gained in forming each ion. a. Br^ b. Na c. As^3 ^ d. Ca^2 e. Cu^ f. H
- Name each ion in Problem 31. Identify each as an anion or a cation.
- Define valence electrons.
- How many electrons does each atom have? What group is each in? a. nitrogen b. lithium c. phosphorus d. barium e. bromine f. carbon
- Write electron dot structures for each of the following elements. a. Cl b. S c. Al d. Li
- How many electrons must each atom lose to attain a noble-gas electron configuration? a. Ca b. Al c. Li d. Ba
- Write the formula for the ion formed when each of the following elements loses its valence electrons. a. aluminum b. lithium c. barium d. potassium e. calcium f. strontium
- Why do nonmetals tend to form anions when they react to form compounds?
- What is the formula of the ion formed when the following elements gain or lose valence electrons and attain noble-gas configurations? a. sulfur b. sodium c. fluorine d. phosphorus
- How many electrons must be gained by each of the following atoms to achieve a stable electron configuration? a. N b. S c. Cl d. P
7.2 Ionic Bonds and Ionic Compounds
- Which of the following pairs of atoms would you expect to combine chemically to form an ionic compound? a. Li and S b. O and S c. Al and O d. F and Cl e. I and K f. H and N
- Identify the kinds of ions that form each ionic compound. a. calcium fluoride, CaF 2 b. aluminum bromide, AlBr 3 c. lithium oxide, Li 2 O d. aluminum sulfide, Al 2 S 3 e. potassium nitride, K 3 N
- Explain why ionic compounds are electrically neutral.
- Which of the following pairs of elements will not form ionic compounds? a. sulfur and oxygen b. sodium and calcium c. sodium and sulfur d. oxygen and chlorine
- Write the formula for the ions in the following compounds. a. KCl b. BaSO 4 c. MgBr 2 d. Li 2 CO 3
- Most ionic substances are brittle. Why?
- Explain why molten MgCl 2 does conduct an electric current although crystalline MgCl 2 does not. 7.3 Bonding in Metals
- Explain briefly why metals are good conductors of electricity.
- Name the three crystal arrangements of closely packed metal atoms. Give an example of a metal that crystallizes in each arrangement.
- Name some alloys that you have used or seen today.
- Explain why the properties of all steels are not identical.
Ionic and Metallic Bonding 209
72. Each dot in the electron dot struc- ture represents a valence electron in the electron configuration diagram. 73. By gaining or losing electrons the atoms of elements achieve a noble- gas electron configuration. 74. An atom of silver has the electron configuration 1 s^22 s^22 p^63 s^23 p^6 3 d^104 s^24 p^64 d^105 s^1. To achieve the configuration of the preceding noble gas, krypton, a silver atom would have to lose eleven elec- trons and form Ag11+. To achieve the configuration of the following noble gas xenon, a silver atom must gain seven electrons and form Ag^7 −. Because ions with such high charges are unlikely, silver does not achieve a noble-gas con- figuration. However, if a silver atom loses its 5 s^1 electron, the result is an outer electron configu- ration of eighteen electrons, writ- ten as 4 s^24 p^64 d^10. This configuration is favored and sta- ble. It is known as a pseudo-noble- gas configuration. 75. No, sodium chloride is composed of equal numbers of sodium ions and chloride ions; the ions are in a 1:1 ratio. Each sodium ion is sur- rounded by chloride ions, and each chloride is surrounded by sodium ions. 76. In sodium chloride crystals the sodium and chloride ions vibrate about fixed points; in the molten state, the ions are free to move. 77. The spheres are more closely packed in (a); there is less empty space in (a), and a rough count shows 25 spheres in (a) compared with 22 spheres in (b). 78. Metals are ductile (can be drawn into wires) and malleable (can be hammered into shapes). These changes are possible because a metal consists of metal cations in a sea of valence electrons. When subjected to pressure, the cations easily slide past one another. 79. Both metals and ionic compounds are com- posed of ions. Both are held together by electrostatic bonds. Metals always conduct electricity, and ionic compounds conduct only when melted or in water solution. Ionic compounds are composed of cations and anions, but metals are composed of cations and free-floating valence electrons. Metals are ductile, but ionic compounds are brittle. 80. a. cation: lose 1e−^ b. cation: lose 1e− c. unreactive d. anion: gain 1e− e. cation: lose 2e− 81. Na+^ and Cs+^ differ greatly in size. Na+^ and Cl−^ are similar in size to Mn2+^ and S^2 −. 82. 0.1445 nm 83. a. Cu, Zn b. Ag, Cu c. Cu, Sn d. Fe, Cr, Ni, C e. Fe, Cr, Ni, Mo f. Fe, Cr, C
Critical Thinking Concept Challenge
Assessment 209
72. What is the relationship between the number of electrons in the valence shells in an electron configuration diagram for an atom and the number of dots in the corresponding electron dot structure? 73. Why are many elements more stable as ions than they are as atoms? 74. Describe the formation of a cation that is an exception to the octet rule. In your description, compare the electron configuration of the cation to the electron configurations of the nearest noble gases. 75. Is it accurate to describe sodium chloride (NaCl) as consisting of individual particles, each made up of one Na^ cation and one Cl^ anion? Explain your answer. 76. How do the motions of sodium ions and chloride ions in molten sodium chloride differ from the motions of these ions in sodium chloride crystals? 77. How atoms and ions are arranged in crystals is not just dependent on size. The spheres in each atomic window below are identical in size. The windows have exactly the same area. In which window are the spheres more closely packed? Explain your reasoning. 80. Classify each atom in the following list. Will each atom form a cation or an anion? Or is it chemi- cally unreactive? For the atoms that do form ions during a chemical reaction, write the number of electrons the atom will gain or lose. a. lithium b. sodium c. neon d. chlorine e. magnesium 81. The chemically similar alkali metal chlorides NaCl and CsCl have different crystal structures, whereas the chemically different NaCl and MnS have the same crystal structures. Why? 82. Silver crystallizes in a face-centered cubic arrangement. A silver atom is at the edge of each lattice point. The length of the edge of the unit cell is 0.4086 nm. What is the atomic radius of silver? 83. List the elements that are used to make each alloy. a. brass b. sterling silver c. bronze d. stainless steel e. surgical steel f. spring steel 78. Two physical properties of metals are ductility and malleability. Explain these properties based on what you know about the valence electrons of metal atoms. 79. Compare and contrast the physical and chemical characteristics of metals and ionic compounds.
a. b.
Sodium chloride (NaCl)
Cl Na
Cl Cs
Cesium chloride (CsCl)
210 Chapter 7
Assessment continued
CHAPTER
84. Organic chemistry is the study of chemicals containing carbon; inorganic chemistry is the study of chemicals that do not contain carbon. 85. an analytical chemist 86. use insulation 87. a, b, and d are chemical changes; c is a physical change 88. b and e; c is not a mixture, it is a pure substance 89. a. liquid, vapor b. vapor c. liquid, vapor d. liquid, vapor 90. a. 56.6 g b. 0.0048 m c. 1.81 L d. 4.0 × 103 mg 91. b 92. –269°C 93. 27.0 cm^3 94. a. b. c. d. 95. 14 amu 96. Each of the isotopes has 8 pro- tons and 8 electrons; oxygen- also has 8 neutrons, oxygen- has 9 neutrons, and oxygen- has 10 neutrons. 97. a. 1 b. 3 c. 1 d. 5 98. a. N, 1 s^2 2 s^2 2 p^3 b. Be, 1 s^2 2 s^2 c. P, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^2 d. K, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^1 99. chlorine, Cl, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^5 100. a. 5 × 10 −^7 m b. the visible region, green 101. a. K, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 4 s^1 b. Al, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^1 c. S, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^4 d. Ba, 1 s^2 2 s^2 2 p^6 3 s^2 3 p^6 3 d^10 4 s^2 4 p^6 4 d^10 5 s^2 5 p^6 6 s^2 102. the electron 103. sodium (Na), cesium (Cs), rubidium (Rb), lithium (Li)
64 30 Zn^
37 17 Cl^
3 1 H 40 20 Ca
210 Chapter 7
7 Assessment continued
84. How is organic chemistry distinguished from inorganic chemistry? (Chapter 1) 85. What is the name given to a chemist who studies the composition of matter? (Chapter 1) 86. Explain an easy way to conserve energy. (Chapter 1) 87. Classify the following as chemical or physical changes. (Chapter 2) a. Cookies are baked. b. A firefly emits light. c. A figure is carved from wood. d. Caramel is made from sugar. 88. Which of the following is not a homogeneous mixture? (Chapter 2) a. gold ring b. spaghetti sauce c. cane sugar d. window glass e. river water f. bottled water 89. What physical state(s) can each of the following substances become as you raise its temperature? (Chapter 2) a. silver b. gasoline c. ice d. wax 90. Round each measurement to the number of significant figures indicated in parentheses. (Chapter 3) a. 56.55 g (3) b. 0.004 849 m (2) c. 1.8072 L (3) d. 4.007 103 mg (2) 91. Which of the following linear measurements is the longest? (Chapter 3) a. 6 104 cm b. 6 106 mm c. 0.06 km d. 6 109 nm 92. Helium has a boiling point of 4 K. This is the lowest boiling point of any liquid. Express this temperature in degrees Celsius. (Chapter 3) 93. The density of silicon is 2.33 g/cm^3. What is the volume of a piece of silicon that has a mass of 62.9 g? (Chapter 3) 94. Express the composition of each atom in short- hand form. (Chapter 4) a. zinc-64 b. chlorine- c. hydrogen-3 d. calcium- 95. An atom of carbon and an atom of element Z together have a mass of 6 amu less than double the mass of an atom of oxygen. If an atom of oxygen has a mass of 16 amu and the mass of an atom of carbon is 12 amu, what is the mass of an atom of element Z? (Chapter 4) 96. Determine the number of protons, electrons, and neutrons in each of the three isotopes of oxygen. (Chapter 4) 97. How many orbitals are in the following sublev- els? (Chapter 5) a. 4 s sublevel b. 2 p sublevel c. 3 s sublevel d. 4 d sublevel 98. Give the symbol for each element and write the electron configuration for each atom. (Chapter 5) a. nitrogen b. beryllium c. phosphorus d. potassium 99. An atom of an element has 17 electrons. Give the name and symbol of the element and write the complete electron configuration. (Chapter 5) 100. A beam of electromagnetic radiation has a wavelength of 500 nm. (Chapter 5) a. What is this wavelength in meters? b. In what region of the spectrum is this? 101. Give the symbol of the element and the com- plete electron configuration of the element found at each location in the periodic table. (Chapter 6) a. Group 1A, period 4 b. Group 3A, period 3 c. Group 6A, period 3 d. Group 2A, period 6 102. Which subatomic particle plays the most important role in chemistry? (Chapter 6) 103. Give the name and symbol of two elements that have properties similar to those of potassium. (Chapter 6)
Cumulative Review
