Unit 4. ATOMIC THEORY
65. What is the definition of an atom? The smallest particle of an element
that retains the properties of that element
66. How does Dalton's atomic theory help to explain the law of conservation
of mass? Part of Dalton’s theory states that atoms cannot be created or
destroyed in ordinary chemical reactions, just rearranged.
67. The electron.
68. Explain Rutherford’s gold foil experiment. What did Rutherford discover
about the structure of the atom? In the experiment, alpha particles (helium
nuclei) were streamed toward a sheet of gold foil. Some of the alpha
particles bounced off of the gold foil. This meant that they were hitting a
dense, relatively large object, which Rutherford called the nucleus.
69. Where are each of subatomic particles located in the atom? Protons and
neutrons: nucleus; electron: electron cloud
What is the charge on each particle? Proton - +1; neutron – 0; electron - -1
70. Why is an atom electrically neutral? Because the number of protons and
electrons are the same and they have the opposite charge, so the positive
and negative charges cancel out.
71. How do isotopes of an element differ? They have different number of
neutrons (which makes their masses different)
72. Define: atomic number the number of protons (what defines an
element) and what the periodic table is organized by;
mass number the sum of the number of protons and neutrons for an
isotope;
atomic mass protons plus neutrons.
73. Calculate the number of protons, neutrons and electrons in the following
isotopes:
(a) Oxygen-18 8 protons, 8 electrons, 10 neutrons
(b) Cadmium-112 48 protons, 48 electrons, 64 neutrons
(c) Tellurium-128 52 protons, 52 electrons, 76 neutrons
(d) Neon-20 10 protons, 10 neutrons and 10 electrons
74. An element is defined by the number of _protons_ it has, also known as
the _atomic number_.
75. Calculate the average atomic mass of an element that is made up of
isotope #1: 27.8 % at 37.0 amu and isotope #2: 73.2% at 35.0 amu. 35.906
amu
76. List the number of orbitals contained in each of the s, p, d, and f sublevels.
s: 1, p: 3, d: 5, f: 7
77. How many electrons can occupy any s sublevel? 2 p? 6 d? 10 f? 14
78. Write electron configurations and orbital (arrow) diagrams for these
elements: B, N, Ne, K
B: 1s2 2s2 2p1 N: 1s2 2s2 2p3 Ne: 1s2 2s2 2p6 K: 1s2 2s2 2p6 3s2 3p6 4s1 ask
teacher for orbital diagrams or see class notes for examples
79. The element with electron configuration 1s2 2s2 2p6 3s2 3p4 is? sulfur
80. What can be said about the properties of elements in the same group or
column in the periodic table? The elements within a group on the PT
have similar properties because the have the same number of valence
electrons and therefore the same ways of bonding
81. Where are the alkali metals on the periodic table? Group 1 Alkaline earth
metals? Group 2 Halogens? Group 17 Noble gases? Group 18
82. Where are the transition metals on the periodic table? The middle section
In what “block” are they found? The “d” block
83. Where are the lanthanides and actinides on the periodic table? at the
bottom
In what “block” are they found? The “f” block
84. Define valence electrons. Electrons located in the outermost energy level,
they are the electrons that are involved in chemical reactions. Explain
how you would find the valence electrons for an element and give an
example. The number of valence electrons equals the number of
electrons in the outermost energy level (it also equals the group number
for the s block and the group number minus 10 for the p block)
85. Draw electron dot diagrams for calcium, oxygen, argon, and phosphorus.
This could not be typed out easily, but your diagrams should show
calcium: 2 dots, oxygen: 6 dots, argon: 8 dots, phosphorus: 5 dots
(Remember, you can’t pair electrons until you have one on each side.)
86. What is nuclear fusion? Forcing 2 nuclei together to form a new element.
Example: 2 Hydrogen atoms make a Helium atom.
87. What is nuclear fission? Breaking a nucleus apart into smaller nuclei.
88. What part of the atom do nuclear reactions take place? The nucleus.
89. What is alpha decay and how do we show it in a nuclear decay problem?
A nucleus of an unstable atom releases 2 protons and 2 neutrons (a
4
Helium nucleus). 2 He
90. What is beta decay and how do we show it in a nuclear decay problem? a
neutron in the original atom decays to form a proton and an electron:
0
1
e
248
91. Solve this Alpha decay equation: 96 Cm
 24 He +
244
94
Pu
203
92. Solve this Beta decay equation: 80 Hg

0
1
203
e + 81Tl