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The Structure of the Atom
Objective 1
Section 4.1
Early Ideas About Matter
In your textbook, read about the philosophers, John Dalton, and defining the atom.
For each statement below, write true or false.
____________________ 1. Ancient philosophers regularly performed controlled experiments.
____________________ 2. Philosophers formulated explanations about the nature of matter based on their
own experiences.
____________________ 3. Both Democritus and Dalton suggested that matter is made up of atoms.
____________________ 4. Dalton’s atomic theory stated that atoms separate, combine, or rearrange in
chemical reactions.
____________________ 5. Dalton’s atomic theory stated that matter is mostly empty space.
____________________ 6. Dalton was correct in thinking that atoms could not be divided into smaller
particles.
____________________ 7. Dalton’s atomic theory stated that atoms of different elements combine in simple
whole-number ratios to form compounds.
____________________ 8. Dalton thought that all atoms of a specific element have the same mass.
____________________ 9. Democritus proposed that atoms are held together by chemical bonds, but no one
believed him.
___________________ 10. Dalton’s atomic theory was based on careful measurements and extensive research.
Section 4.2
Defining the Atom
In your textbook, read about the electron and the nuclear atom.
For each item in Column A, write the letter of the matching item in Column B.
Column A
Column B
_________11. Proposed the nuclear atomic model
a. Thomson
_________12. Determined the mass-to-charge ratio of an electron
b. Millikan
_________13. Calculated the mass of an electron
c. Rutherford
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Objective 2
In your textbook, read about the discovery of protons and neutrons.
Complete the following table of proton, electron, and neutron characteristics.
Particle
Symbol
Location
Relative Charge
Relative Mass
1. Proton
2.
n
1/1840
3.
Section 4.3
How Atoms Differ
In your textbook, read about atomic number.
For each statement below, write true or false.
_____________________ 4. The number of neutrons in an atom is referred to as its atomic number.
_____________________ 5. The periodic table is arranged by increasing atomic number.
_____________________ 6. Atomic number is equal to the number of electrons in an atom.
_____________________ 7. The number of protons in an atom identifies it as an atom of a particular
element.
_____________________ 8. Most atoms have either a positive or a negative charge.
Answer the following questions.
9. Lead has an atomic number of 82. How many protons and electrons does lead have?
______________________________________________________________________________________________
10. Oxygen has 8 electrons. How many protons does oxygen have? ____________________
11. Zinc has 30 protons. What is its atomic number? ______________________
12. Astatine has 85 protons. What is its atomic number? ______________________
13. Rutherfordium has an atomic number of 104. How many protons and electrons does it have?
______________________________________________________________________________________________
14. Polonium has an atomic number of 84. How many protons and electrons does it have?
______________________________________________________________________________________________
15. Nobelium has an atomic number of 102. How many protons and electrons does it have?
______________________________________________________________________________________________
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In your textbook, read about isotopes and mass number.
Determine the number of protons, electrons, and neutrons for each isotope described below.
16. An isotope has atomic number 19 and mass number 39.
______________________________________________________________________________________________
17. An isotope has 14 electrons and a mass number of 28.
______________________________________________________________________________________________
18. An isotope has 21 neutrons and a mass number of 40.
______________________________________________________________________________________________
19. An isotope has an atomic number 51 and a mass number 123.
______________________________________________________________________________________________
Answer the following question.
20. Which of the isotopes in problems 13–16 are isotopes of the same element? Identify the element.
______________________________________________________________________________________________
Write each isotope below in symbolic notation. Use the periodic table to determine the atomic
number of each isotope.
21. neon-22 ______________
23. cesium-133 ______________
22. helium ______________
24. uranium-234 _______________
Label the mass number and the atomic number on the following isotope notation.
25. ___________________
26. ___________________
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Mg
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Objective 3
Section 4.4
Unstable Nuclei and Radioactive Decay
In your textbook, read about radioactivity.
For each item in Column A, write the letter of the matching item in Column B.
Column A
________ 1.
Column B
a. nuclear reaction
The rays and particles that are emitted by a radioactive material
________ 2. A reaction that involves a change in an atom’s nucleus
b. beta radiation
________ 3. The process in which an unstable nucleus loses energy spontaneously
c. radiation
d. radioactive decay
________ 4. Fast-moving electrons
In your textbook, read about types of radiation.
Use the diagram to answer the questions.
5. Which plate do the beta particles bend toward? Explain.
______________________________________________________________________________________________
6. Explain why the gamma rays do not bend.
______________________________________________________________________________________________
7. Explain why the path of the beta particles bends more than the path of the alpha particles.
______________________________________________________________________________________________
______________________________________________________________________________________________
Complete the following table of the characteristics of alpha, beta, and gamma radiation.
Radiation Type
8. Alpha
9.
10.
Composition
Symbol
Mass (amu)
Charge
1/1840
High-energy electromagnetic radiation
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Section 24.1
Nuclear Radiation
In your textbook, read about the terms used to describe nuclear changes.
Use each of the terms below just once to complete the passage.
alpha particle
radioactivity
gamma ray
radioisotope
beta particles
radiation
X-ray
radioactive decay
The discovery of the (11) ___________________ in 1895 by Wilhelm Roentgen opened a
whole new field of research. Among those who worked in this new field were Pierre and Marie
Curie. The Curies discovered that some forms of matter give off (12) ________________, a
combination of particles and energy. Marie Curie named this process (13) ________________
Another term used to describe the process by which one element spontaneously changes into
another element is (14) ____________________. Any isotope that undergoes such changes is
called a(n) (15)___________________.
There are three common forms of radiation. One type is a form of energy known as
(16) ________________. The other types of radiation consist of particles. The form of radiation
containing the heavier particle is made up of helium nuclei called (17) ___________________. The form
of radiation containing the lighter particle consists of electrons called
(18) ____________________.
Section
24.2 Radioactive Decay
In your textbook, read about the changes that take place in an atomic nucleus when it decays.
Circle the letter of the choice that best completes the statement.
19. The number of stable isotopes that exist compared to the number of unstable isotopes is
a. much less.
b. much more.
c. slightly more.
d. about the same.
20. The isotope formed by the beta decay of
a. 18.
40
19
b. 39.
21. The isotope formed by the alpha decay of
a. 234.
22. When the isotope
a.
234
89
150
66
c. 20.
238
92
238
91
d. 21.
U has a mass number of
b. 236.
c. 238.
d. 240.
Pa decays by beta emission, the isotope formed is
Ac .
b.
238
90
Th .
23. The isotope formed by the alpha decay of
a.
K has an atomic number of
Dy .
Chemistry: Matter and Change
b.
150
67
Ho .
154
66
c.
237
92
U.
d.
238
92
U.
c.
150
64
Gd .
d.
154
67
Ho .
Dy is
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24. The decay of
a.
4
2
Section
162
69
Tm Tm yields
He .
162
68
Er and
b. e–.
c. .
d. e+ .
24.3 Nuclear Reactions
In your textbook, read about the process of induced nuclear transmutation.
For each statement below, write true or false.
___________________
25.
Transmutation is the conversion of an atom of one element to an atom of
another element.
___________________ 26.
All nuclear reactions involve some type of nuclear transmutation.
___________________
27.
Scientists induce transmutations by bombarding stable nuclei with highenergy alpha, beta, or gamma radiation.
___________________
28.
The half-life of a radioisotope is the time it takes for that isotope to
decay.
___________________
29.
A radioisotope that decays very rapidly has a short half-life.
___________________
30.
Radioisotopes with very long half-lives are seldom found in Earth’s
crust.
___________________
31.
Mass number and atomic number are conserved in all nuclear reactions.
___________________
32.
The mass of a 25.0 g piece of
3.1 g after 7.2 hr.
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238
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Cm (half-life: 2.4 hr) will be reduced to
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Objective 4
Average Atomic Mass
In your textbook, read about mass of individual atoms.
Circle the letter of the choice that best completes the statement.
1. The mass of an electron is
a. smaller than the mass of a proton.
b. smaller than the mass of a neutron.
c. a tiny fraction of the mass of an atom.
d. all of the above.
2. One atomic mass unit is
a. 1/12 the mass of a carbon-12 atom.
b. 1/16 the mass of an oxygen-16 atom.
c. exactly the mass of one proton.
d. approximately the mass of one proton plus one neutron.
3. The atomic mass of an atom is usually not a whole number because it accounts for
a. only the relative abundance of the atom’s isotopes.
b. only the mass of each of the atom’s isotopes.
c. the mass of the atom’s electrons.
d. both the relative abundance and the mass of each of the atom’s isotopes.
Use the figures to answer the following questions.
4. What is the atomic number of osmium? _____________________
5. What is the chemical symbol for niobium? _______________________
6. What is the atomic mass of osmium? ____________________
7. What units is the atomic mass reported in? ____________________
8. How many protons and electrons does an osmium atom have? A niobium atom?
______________________________________________________________________________________________
Calculate the atomic mass of each element described below. Then use the periodic table to identify
each element.
9.
Isotope
63
65
Mass (amu)
Percent Abundance
X
62.930
69.17
X
64.928
30.83
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10.
Isotope
35
37
Mass (amu)
Percent Abundance
X
34.969
75.77
X
36.966
24.23
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