47374_04_p25-32.qxd 2/9/07 7:50 AM Page 25. 4 Atoms and Elements

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 25 4 Atoms and Elements 4.1 a. Cu b. Si c. K d. N e. Fe f. Ba g. Pb h. Sr 4.2 a. O b. Li c. S d. Al e. H f. Ne g. Sn h. Au 4.3 a. carbon b. chlorine c. iodine d. mercury e. fluorine f. argon g. zinc h. nickel 4.4 a. helium b. phosphorus c. sodium d. magnesium e. calcium f. bromine g. cadmium h. silicon 4.5 a. sodium (Na) and chlorine (Cl) b. calcium (Ca), sulfur (S), and oxygen (O) c. carbon (C), hydrogen (H), chlorine (Cl), nitrogen (N), and oxygen (O) d. calcium (Ca), carbon (C), and oxygen (O) 4.6 a. hydrogen (H) and oxygen (O) b. sodium (Na), hydrogen (H), carbon (C), and oxygen (O) c. sodium (Na), oxygen (O), and hydrogen (H) d. carbon (C), hydrogen (H), and oxygen (O) 4.7 a. C, N, and O are in Period 2. b. He is the element at the top of Group 8A (18). c. The alkali metals are the elements in Group 1A (1). d. Period 2 is the horizontal row of elements that ends with neon (Ne). 4.8 a. Group 1A (1) b. Period 2 c. Group 8A (18) d. Group 7A (17) 4.9 a. alkaline earth metal b. transition element c. noble gas d. alkali metal e. halogen 4.10 a. noble gas b. alkaline earth metal c. transition element d. halogen e. alkaline earth metal 4.11 a. C b. He c. Na d. Ca e. Al 4.12 a. Be b. P c. Kr d. I e. Ge 4.13 On the periodic table, metals are located to the left of the heavy zigzag line, nonmetals are elements to the right, and metalloids (B, Si, Ge, As, Sb, Te, Po, and At) are located along the line. a. metal b. nonmetal c. metal d. nonmetal e. nonmetal f. nonmetal g. metalloid h. metal 4.14 a. metal b. metal c. nonmetal d. metalloid e. nonmetal f. nonmetal g. nonmetal h. metal 4.15 a. electron b. proton c. electron d. neutron 4. a. neutron b. proton and neutron c. electron d. electron 4.17 Rutherford determined that the two most massive subatomic particles, protons and neutrons, are located in a very small, central region of the atom called the nucleus. 25

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 26 Chapter 4 4.18 Because protons are present in the nucleus of every element and protons are the positively charged subatomic particles. 4.19 Selection b (a proton and an electron) is the only one with a pair of particles having opposite charges. 4.20 Answers a (two protons) and c (two electrons) are pairs of particles having the same charge. 4.21 In the process of brushing your hair on a dry day, unlike charges that attract develop on the hair and brush. 4.22 Because the clothes cling to each other, there must be opposite (unlike) electrical charges on the clothing. 4.23 The atomic number is equal to the number of protons. The mass number is the sum of the protons and neutrons. a. atomic number b. both c. mass number d. atomic number 4.24 a. number of protons and electrons, if a neutral atom b. number of particles (protons plus neutrons) in the nucleus c. number of neutrons d. nothing useful 4.25 a. lithium, Li b. fluorine, F c. calcium, Ca d. zinc, Zn e. neon, Ne f. silicon, Si g. iodine, I h. oxygen, O 4.26 a. hydrogen, H b. sodium, Na c. potassium, K d. iron, Fe e. bromine, Br f. silver, Ag g. phosphorus, P h. helium, He 4.27 a. 12 b. 30 c. 53 d. 19 4.28 a. 6 b. 9 c. 20 d. 4.29 Name Atomic Mass Number Number of Number of of Element Symbol Number Number of Protons Neutrons Electrons Aluminum Al 13 27 13 14 13 Magnesium Mg 12 24 12 12 12 Potassium K 19 39 19 20 19 Sulfur S 31 15 Iron Fe 26 56 26 30 26 4.30 Name Atomic Mass Number Number of Number of of Element Symbol Number Number of Protons Neutrons Electrons Nitrogen N 7 15 7 8 7 Calcium Ca 20 42 20 22 20 Strontium Sr 38 88 38 50 38 Silicon Si 14 30 14 14 Barium Ba 56 138 56 82 56 4.31 a. Because the atomic number of aluminum is 13, every Al atom has 13 protons. An atom of aluminum (mass number 27) has 14 neutrons (27 13 14 n). Neutral atoms have the same number of protons and electrons: 13 protons, 14 neutrons, and 13 electrons. 26

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 27 b. Because the atomic number of chromium is 24, every Cr atom has 24 protons. An atom of chromium (mass number 52) has 28 neutrons (52 24 28 n). Neutral atoms have the same number of protons and electrons: 24 protons, 28 neutrons, and 24 electrons. c. Because the atomic number of sulfur is, every S atom has protons. An atom of sulfur (mass number 34) has 18 neutrons (34 18 n). Neutral atoms have the same number of protons and electrons: protons, 18 neutrons, and electrons. d. Because the atomic number of iron is 26, every Fe atom has 26 protons. An atom of iron (mass number 56) has 30 neutrons (56 26 30 n). Neutral atoms have the same number of protons and electrons: 26 protons, 30 neutrons, and 26 electrons. 4.32 a. 1 proton, 1 neutron, 1 electron b. 7 protons, 7 neutrons, 7 electrons c. 14 protons, 12 neutrons, 14 electrons d. 30 protons, 40 neutrons, 30 electrons 31 80 27 35 4.33 a. 15P b. 35Br c. 13Al d. 17Cl 18 9 56 24 4.34 a. 8 O b. 4Be c. 26Fe d. 11Na 32 33 34 36 4.35 a. S S S S b. They all have the same atomic number (the same number of protons and electrons). c. They have different numbers of neutrons, which is reflected in their mass numbers. d. The atomic mass of sulfur on the periodic table is the average atomic mass of all the naturally occurring isotopes of sulfur. 84 86 87 88 4.36 a. 38Sr 38Sr 38Sr 38Sr b. They all have the same atomic number (the same number of protons and electrons). c. They have different numbers of neutrons, which is reflected in their mass numbers. d. The atomic mass of strontium on the periodic table is the average atomic mass of all the naturally occurring isotopes of strontium. 4.37 The mass of an isotope is the mass of an individual atom. The atomic mass is the weighted average of all the naturally occurring isotopes of that element. 4.38 The mass number gives the number of protons and neutrons in an atom; the atomic number gives the number of protons. 63 4.39 Because the atomic mass of copper is closer to 63 amu, there are more atoms of Cu. 4.40 The mass of F on the periodic table should be very close to 19 amu. 56 4.41 Because the atomic mass of iron is 55.85 amu, the most abundant isotope is Fe. 4.42 The atomic mass of Zn is the weighted average of the masses of the five isotopes. 4.43 68.926 amu 60.10 100 70.925 amu 39.90 100 69.72 amu Atoms and Elements 4.44 63.55 amu 4.45 The electrons surrounding a nucleus have specific energies. Electrons with similar energies will be found grouped together within a specific energy level. 4.46 The first energy level is filled with 2 electrons. The second energy level can hold a maximum of 8 electrons. Because we are only considering the first 20 elements, the third energy level will have 8 electrons and the fourth energy level will have only 2 electrons in it. 4.47 a. 8 b. 5 c. 8 d. 0 e. 8 4.48 a. 0 b. 6 c. 5 d. 8 e. 0 27

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 28 6 e Chapter 4 4.49 a. 2, 4 b. 2, 8, 8 c. 2, 8, 6 d. 2, 8, 4 e. 2, 8, 3 f. 2, 5 4.50 a. 2, 8, 5 b. 2, 8 c. 2, 6 d. 2, 8, 8 e. 2, 8, 3 f. 2, 8, 4 4.51 a. Li b. Mg c. H d. Cl e. O 4.52 a. N b. S c. C d. Ar e. Al 4.53 a. boron, B: 2, 3 aluminum: 2, 8, 3 b. 3 c. Group 3A (13) 4.54 a. fluorine, F: 2, 7 chlorine: 2, 8, 7 b. 7 c. Group 7A (17) 4.55 a. 2 e, Group 2A (2) b. 7 e, Group 7A (17) c., Group 6A () d. 5 e, Group 5A (15) e. 2 e, Group 2A (2) f. 7 e, Group 7A (17) 4.56 a. 1 e, Group 1A (1) b. 4 e, Group 4A (14) c. 8 e, Group 8A (18) d. 8 e, Group 8A (18) e. 4 e, Group 4A (14) f. 1 e, Group 1A (1) 4.57 The number of dots is equal to the number of valence electrons as indicated by the group number. a. Sulfur has 6 valence electrons S Group 6A () b. Nitrogen has 5 valence electrons N Group 5A (15) c. Calcium has 2 valence electrons Ca Group 2A (2) d. Sodium has 1 valence electron Na Group 1A (1) e. Potassium has 1 valence electron K Group 1A (1) 4.58 a. 4A (14), C b. 6A (), O c. 7A (17), F d. 1A (1), Li e. 7A (17), Cl 4.59 a. M b. M 4.60 a. Nm b. Nm 4.61 Alkali metals are members of Group 1A (1), and each has 1 valence electron. 4.62 Halogens are members of Group 7A (17), and each has 7 valence electrons. 4.63 a. The ionization energy decreases going down a group: Br, Cl, F b. Going across a period from left to right, the ionization energy generally increases: Na, Al, Cl c. The ionization energy decreases going down a group: Cs, K, Na 4.64 a. C, O, N b. S, P, Cl c. As, P, N 4.65 a. Br, which is above I in Group 7A (17), has a higher ionization energy than I. b. Al has a higher ionization energy than K because ionization energy increases going left to right and decreases going down a group. c. P has a higher ionization energy than Si because ionization energy increases going left to right across a period. 4.66 a. Ne b. Br c. Ca 4.67 a. false b. true c. true d. false 4.68 a. X is Cl, chlorine. This isotope has 17 protons and 20 neutrons. b. X is Fe, iron. This isotope has 26 protons and 30 neutrons. c. X is Sn, tin. This isotope has 50 protons and 66 neutrons. d. X is Sn, tin. This isotope has 50 protons and 74 neutrons. e. X is Cd, cadmium. This isotope has 48 protons and 68 neutrons. c and d are both isotopes of Sn, tin. 28

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 29 4.69 a. Both have 20 neutrons. b. Both have protons. c. Not the same. d. Both have 22 neutrons. 4.70 28 Si Isotope 29 Si Atoms and Elements Number of protons 14 14 14 Number of neutrons 14 15 Number of electrons 14 14 14 Atomic number 14 14 14 Mass number 28 29 30 4.71 a. 9 4Be b. 11 5 B c. 13 6 C 10 d. 5 B e. 12 6 C The atoms b and d are isotopes of boron; c and e are isotopes of carbon. 4.72 a. metal b. metalloid c. nonmetal d. metalloid e. nonmetal 4.73 a. 3, Li b. 86, Rn c. 24.31, Mg d. 19.00, F 4.74 a. 32, Ge b. 83, Bi c. 39.10 amu, K d. 210, At 4.75 Any element with a two-letter symbol has the first letter capitalized and the second letter in lowercase. CO would indicate a compound made of the two elements carbon and oxygen. 4.76 a. Incorrect. The symbol for copper is Cu. b. Incorrect. The symbol for silicon is Si. c. Correct as written. d. Incorrect. The symbol for fluorine is F. e. Incorrect. The symbol for potassium is K. f. Correct as written. g. Correct as written. h. Incorrect. The symbol for lead is Pb. 4.77 a. Mg, magnesium b. Br, bromine c. Al, aluminum d. O, oxygen 4.78 a. Group 1A (1), Period 4 b. Group 5A (15), Period 3 c. Group 4A (14), Period 2 d. Group 8A (18), Period 2 4.79 Any two of the following in each part are correct responses: a. Group 7A (17), fluorine, chlorine, bromine, iodine, or astatine b. Group 8A (18), helium, neon, argon, krypton, xenon, or radon c. Group 1A (1), lithium, sodium, potassium, rubidium, cesium, or francium, but not hydrogen d. Group 2A (2), beryllium, magnesium, calcium, strontium, barium, or radium 4.80 a. metal b. metal c. metal d. nonmetal e. metal f. nonmetal 4.81 a. False. A proton has a positive charge. b. False. The neutron has about the same mass as a proton. c. True d. False. The nucleus is the tiny, dense, central core of an atom. e. True 4.82 a. True b. True c. False. The charge of the electron is equal but opposite to the charge of the proton. d. False. The proton and the neutron have about the same mass. e. False. The atomic number is the number of protons. 4.83 a. protons b. protons c. alkali metals 4.84 a. mass b. halogens c. metals 30 Si 29

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 30 Chapter 4 4.85 a. lithium, Li b. fluorine, F c. calcium, Ca d. arsenic, As e. tin, Sn f. cesium, Cs g. gold, Au h. oxygen, O 4.86 a. hydrogen, H b. sodium, Na c. chromium, Cr d. iron, Fe e. bromine, Br f. silver, Ag g. bismuth, Bi h. uranium, U 4.87 a. 25 protons, 25 electrons b. 30 protons, 30 electrons c. 53 protons, 53 electrons d. 12 protons, 12 electrons e. 19 protons, 19 electrons 4.88 a. 6 protons, 6 electrons b. 20 protons, 20 electrons c. 27 protons, 27 electrons d. 17 protons, 17 electrons e. 48 protons, 48 electrons 4.89 a. 13 protons, 14 neutrons, 13 electrons b. 24 protons, 28 neutrons, 24 electrons c. protons, 18 neutrons, electrons d. 26 protons, 30 neutrons, 26 electrons e. 54 protons, 82 neutrons, 54 electrons 4.90 a. 10 protons, 12 neutrons, 10 electrons b. 53 protons, 74 neutrons, 53 electrons c. 35 protons, 40 neutrons, 35 electrons d. 55 protons, 78 neutrons, 55 electrons e. 78 protons, 117 neutrons, 78 electrons 4.91 a. 9 Be b. 26 Mg c. 46 Ca 70 d. Zn e. 63 Cu 4.92 a. 27 Al b. 58 Fe c. 88 Sr 72 d. As 4.93 Nuclear Number of Number of Number of Name Symbol Protons Neutrons Electrons 34 Sulfur S 18 70 Zinc 30Zn 30 40 30 26 Magnesium 12Mg 12 14 12 220 Radon 86Rn 86 134 86 4.94 Nuclear Number of Number of Number of Name Symbol Protons Neutrons Electrons Potassium 41 19K 19 22 19 51 Vanadium 23V 23 28 23 112 Cadmium 48Cd 48 64 48 138 Barium 56Ba 56 82 56 4.95 a. 26 protons, 30 neutrons, 26 electrons 51 b. 26Fe 51 c. 24Cr 4.96 No. The atomic mass is the weighted average of the eight naturally occurring isotopic masses. 4.97 a. 17 18 All have 8 protons. b. 17 18 All are isotopes of oxygen. c. 9 X Both have mass number of. 18 18 10X Both have mass number of 18. 18 d. Both have 8 neutrons. 30 10X

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 31 64 66 67 68 70 4.98 a. 30Zn 30Zn 30Zn 30Zn 30Zn b. All these isotopes contain 30 protons and 30 electrons. Zinc-64 contains 34 neutrons, zinc-66 contains 36 neutrons, zinc-67 contains 37 neutrons, zinc-68 contains 38 neutrons, and zinc-70 contains 40 neutrons. 4.99 a. 82 protons, 126 neutrons, 82 electrons b. 214 Pb c. 214 Bi, bismuth 4.100 a. 47 protons, 60 neutrons, 47 electrons b. 109 Ag c., cadmium 109 Cd Atoms and Elements 4.101 a. N, Group 5A (15), electron arrangement 2, 5 b. Na, Group 1A (1) electron arrangement 2, 8, 1 c. S, Group 6A (), electron arrangement 2, 8, 6 d. B, Group 3A (13), electron arrangement 2, 3 4.102 a. C, Group 4A (14), electron arrangement 2, 4 b. Si, Group 4A (14), electron arrangement 2, 8, 4 c. P, Group 5A (15), electron arrangement 2, 8, 5 N Na S B C Si P d. Ar, Group 8A (158), electron arrangement 2, 8, 8 Ar 4.103 Calcium has a greater net nuclear charge than K. The least tightly bound electron in Ca is further from the nucleus than in Mg and needs less energy to remove. 4.104 The least tightly bound electron in Cl is further from the nucleus than in F and needs less energy to remove. Chlorine has 7 protons and sulfur has 6, so it is easier to remove the valence electron from sulfur. 4.105 a. Na is on the far left of the heavy zigzag line. Na is a metal. b. F at the top of Group 7A (17) and to the far right in Period 2 has the highest ionization energy. c. Na has the lowest ionization energy and loses an electron most easily. d. Cl is found in Period 3 in Group 7A (17). 4.106 a. Kr b. Ca c. Kr d. Ca 4.107 4.108 4.109 27.977 amu 92.23 4.68 28.976 amu 100 100 25.80 amu 1.36 amu 0.9262 amu 28.09 amu 4.110 1.40 /100 203.97 amu 24.10 /100 205.97 amu 22.10/100 206.98 amu 52.40/100 207.98 amu 207.22 amu 43.0 /100 112.90 amu 95.70 /100 M 115 114.8 amu M 115 119.7 amu 29.974 amu 3.09 100 42.70 /100 122.90 amu 57.30 /100 M 121 121.75 amu M 121 120.89 amu 31

47374_04_p25-32.qxd 2/9/07 7:50 AM Page 32 Chapter 4 4.111 1 in. 2.54 cm 1 in. 4.112 200 cm 3 11.3 g cm 3 1 atom 3.14 10 8 cm 8.09 107 atoms 1 atom 3.4 10 22 g 6.6 1022 atom 32