Ch 4 questions
38. Matter is anything that occupies space and has mass. Example: desk, chair
39. protons, neutrons; positive charge equal to the number ofprotons
40. evenly through a sphere
41. They would only be slightly deflected.
42. a. Electron cloud b. protons c. neutron
44. The number of protons equals the number of electrons.
45. 89+
46. protons and neutrons
47. 1836
51. Rutherford aimed a beam of alpha particles at a thin foil of gold. He expected most of the
alpha particles to pass through the gold atoms, confirming the plum pudding model. However,
a few particles were deflected at very large angles, which led to the discovery of the positively
charged nucleus.
52. The α particles were deflected by the positively charged gold nuclei.
53. The cathode ray was attracted to the positive end of the magnet implying that the cathode
ray is negative.
54. attraction to the positively charged nucleus
58. differ: number of neutrons, masses; similar: chemical properties, number of protons and
neutrons
59. They are all equal.
60. mass number = number of p + number of n
61. number of no = mass number – atomic number
62. superscript = mass number (40) and subscript = atomic number (19)
63. amu = 1/12 of the mass of a C-12 atom. It’s a relative standard that is closer in size to
atomic and subatomic masses.
64. Yes; isotopes are atoms of the same element with different atomic mass but the same
number of protons.
66. 44 protons, 44 electrons
67. 6 neutrons
68. mass number is 200
69. mass number is 131
70. 18 protons
71. S = (31.972amu)(0.9502) + (32.971amu)(0.0075) + (33.968 amu)(0.0421) + (35.967
amu)(0.0002) = 32.065 amu
72.
Element
Atomic Number
Mass Number
Protons
Neutrons
Electrons
Cl
17
35
17
18
17
Cl
17
37
17
20
17
73. a. 55 electrons, 55 protons, 77 neutrons
b. 27 electrons, 27 protons, 32 neutrons
c. 69 electrons, 69 protons, 94 neutrons
d. 30 electrons, 30 protons, 40 neutrons
74. a. 31 electrons, 31 protons, 38 neutrons
b. 9 electrons, 9 protons, 14 neutrons
c. 22 electrons, 22 protons, 26 neutrons
d. 73 electrons, 73 protons, 108 neutrons
75. a. 23, 23 b. 25, 25 c. 77. 77 d. 16, 16
Zr
40
90
40
50
40
Zr
40
92
40
52
40
76. Ga-69 must be more abundant because the atomic mass of gallium is closer to the mass of
Ga-69 then the mass of Ga-71.
77. 107.86 amu
78. 51.99 amu
79. Radioactive decay occurs when unstable nuclei spontaneously (without input of energy)
lose energy by emitting radiation.
80. The stability of atoms depends on their neutrons-to-proton ratio. When this ratio is either
too large or too small the nucleus of an atom becomes unstable causing an atom to be
radioactive.
81. by emitting radiation or a particle
82. alpha particle: helium atom with a 2+ charge; beta particle: electron; gamma rays: high
energy radiation
83. symbol
Mass
α: 24He
4
Charge
β
ϒ
1/1840
0
-1
0
+2
84. nuclear reaction
85. α, mass number decreases by 5; β, no change in mass number; ϒ no change in mass
number
86. the neutron-to-proton ratio
87. Radioactivity results when unstable nuclei emit energy in order to gain stability.
88. stable, nonradioactive atom must be formed
89.
55
10
5 B
→ 36Li + 24He
137Cs
→ 56137Ba + -10e