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Chapter 4 Atomic Structure
Multiple Choice (2PTS EACH)
Identify the choice that best completes the statement or answers the question.
1. Which of the following is true about subatomic particles?
A. The mass of a neutron nearly equals the mass of a proton. B. Neutrons have no charge and are the lightest
subatomic particle. C. Electrons are negatively charged and are the heaviest subatomic particle. D. Protons are
positively charged and the lightest subatomic particle.
2. Which pair of atoms constitutes a pair of isotopes of the same element?
20
21
X
X
A. 14 X 14 X B. 17 X 17 X C. 14 X 12 X D. 19 X 19 X E.
6
7
9
8
6
6
10
9
10
11
3. Which item best represents Thomson’s mental image of an atom?
A. a bowling ball B. a sponge C. a chocolate-chip cookie D. a beach ball
4. Which of the following is NOT a part of Dalton's atomic theory?
A. Atoms that combine do so in simple whole-number ratios. B. Atoms are always in motion. C. All elements
are composed of atoms. D. Atoms of the same element are identical.
5. Who conducted experiments to determine the quantity of charge carried by an electron?
A. Millikan B. Thomson C. Rutherford D. Dalton
6. Which of the following was NOT among Democritus’s ideas?
A. Atoms retain their identity in a chemical reaction. B. Atoms are indestructible. C. Atoms are indivisible.
D. Matter consists of tiny particles called atoms.
7. Which particles have almost the same mass?
A. proton and neutron B. all three particles C. proton and electron D. electron and neutron
8. Which of the following isotopes has the same number of neutrons as phosphorus-31?
A. 32
S B. 32
P C. 29
Si D. 28
Si
16
15
14
14
9. In which of the following sets is the symbol of the element, the number of protons, and the number of electrons
given correctly?
A. Cs, 55 protons, 132.9 electrons B. In, 49 protons, 49 electrons C. Zn, 30 protons, 60 electrons D. F, 19
protons, 19 electrons
10. The average atomic mass of an element is the average of the atomic masses of its
A. two most abundant isotopes. B. naturally occurring isotopes. C. artificial isotopes. D. radioactive
isotopes.
11. Which item best represents Dalton’s mental image of an atom?
A. a cork B. a marble C. a balloon full of air D. a candy bar with nuts
12. Which of the following was originally a part of Dalton's atomic theory, but had to be revised about a century ago?
A. Atoms of different elements can combine with one another in simple whole number ratios. B. Compounds
are made by combining atoms. C. Atoms of the same element are identical. D. Atoms are tiny indivisible
particles.
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ID: A
13. Which isotope has 45 neutrons?
A. 78 Se B. 103 Rh C. 80 Kr D. 34 Cl E. 80 Br
34
45
36
17
35
14. Select the correct symbol for an atom of tritium.
A. 11 H B. 31 H C. 21 H D. 10 n
15. Rutherford’s gold foil experiment provided evidence for which of the following statements?
A. Negative and positive charges are spread evenly throughout an atom. B. There is a dense, positively charged
mass in the center of an atom. C. Alpha particles have a positive charge. D. Gold is not as dense as previously
thought.
16. Rutherford conducted an experiment in which he bombarded thin sheets of gold foil with alpha particles. What
were the conclusions from his experiment?
A. The atom has a large, dense negatively charged nucleus. B. The atom is mostly empty space and has a small,
negatively charged nucleus. C. The atom is mostly empty space and has a small, positively charged nucleus.
D. The atom has a large, dense positively charged nucleus.
17. All atoms are ____.
A. neutral, with the number of protons equaling the number of electrons, which is equal to the number of neutrons
B. neutral, with the number of protons equaling the number of electrons C. negatively charged, with the number
of electrons exceeding the number of protons D. positively charged, with the number of protons exceeding the
number of electrons
18. How many protons, electrons, and neutrons does an atom with atomic number 50 and mass number 125 contain?
A. 70 neutrons, 75 protons, 50 electrons B. 75 electrons, 50 protons, 50 neutrons C. 120 neutrons, 50 protons,
75 electrons D. 50 protons, 50 electrons, 75 neutrons
19. Which of the following equals one atomic mass unit?
A. one-twelfth the mass of one carbon-12 atom B. the mass of one electron C. the mass of one carbon-12
atom D. the mass of one helium-4 atom
20. An atom of the most common isotope of gold, 197Au, has __________ protons, __________ neutrons, and
__________ electrons.
A. 79, 118, 79 B. 79, 197, 197 C. 118, 79, 39 D. 197, 79, 118 E. 79, 118, 118
21. If E is the symbol for an element, which two of the following symbols represent isotopes of the same element?
1. 20
E
2. 20
E
3. 219 E
4. 21
E
10
11
10
A. 2 and 3 B. 3 and 4 C. 1 and 4 D. 1 and 2
22. Which of the following is correct concerning subatomic particles?
A. The neutron was discovered by Chadwick in 1932. B. Cathode rays were found to be made of protons.
C. The proton was discovered by Thomson in 1880. D. The electron was discovered by Goldstein in 1886.
23. There are __________ electrons, __________ protons, and __________ neutrons in an atom of 132 Xe.
54
A. 78, 78, 54 B. 54, 54, 132 C. 54, 54, 78 D. 132, 132, 54 E. 78, 78, 132
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ID: A
True/False (2PTS EACH)
Indicate whether the statement is true or false.
24. Except for hydrogen-1, the atomic number of an isotope is always greater than the mass number.
25. The number of electrons in an atom must equal the number of neutrons.
26. The mass of an electron is about equal to the mass of a proton.
27. An element can be identified by the number of protons in its nucleus.
28. The idea of the atom was first proposed by Dalton.
29. The mass number of an element can be used to determine the number of electrons in an atom.
Ag, 107 represents the atomic number and 47 represents the atomic mass of silver.
30. In the notation 107
47
Short Answer (4 PTS EACH: 1 PT FOR CORRECT ANSWER AND 3 PTS FOR CORRECT WORK)
You must show your work for full credit.
31. A fictitious element X is composed of 10.0 percent of the isotope 55 X, 20.0 percent of the isotope 56 X, and the rest
of the isotope 57 X. Calculate the atomic mass of element X. Report final answer to 1 decimal place.
32. Consider an element Z that has two naturally occurring isotopes with the following percent abundances: the
isotope with a mass number of 19.0 is 55.0% abundant; the isotope with a mass number of 21.0 is 45.0%
abundant. What is the average atomic mass for element Z? Report final answer to 1 decimal place.
33. The average atomic weight of copper, which has two naturally occurring isotopes, is 63.5. One of the isotopes has
an atomic weight of 62.9 amu and constitutes 69.1% of the copper isotopes. The atomic weight (amu) of the
second isotope is __________ amu? Report final answer to 1 decimal place.
34. ACC CHEMISTRY ONLY! 5 BONUS PTS FOR REG CHEMISTRY.
Vanadium has two naturally occurring isotopes, 50V with an atomic mass of 49.9472 amu and 51V with an atomic
mass of 50.9440. The atomic weight of vanadium is 50.9415. The percent abundances of the vanadium isotopes
are __________% 50V and __________% 51V. Decimal abundance should have 4 decimal places and percent
abundance should have 2 decimal places.
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ID: A
Chapter 4 Atomic Structure
Answer Section
MULTIPLE CHOICE
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
A
C
C
B
A
A
A
A
B
B
B
D
E
B
B
C
B
D
A
A
C
A
C
MODIFIED TRUE/FALSE
24.
25.
26.
27.
28.
29.
30.
F, less
F, protons
F, neutron
T
F, ancient Greeks
F, atomic number
F, atomic mass
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ID: A
SHORT ANSWER
31. 10.0% × 55 amu = 5.5 amu
20.0% × 56 amu = 11.2 amu
70.0% × 57 amu = 39.9 amu
______________________
= 56.6 amu
32. 19.9 amu
33. 64.8
34. 99.75 and 0.25
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