Chapter 30 Sample Multiple Choice Problems

1. The atomic mass unit is defined as

a. the mass of a proton.

b. the mass of an electron.

c. the mass of a hydrogen-1 atom.

d. one twelfth the mass of a carbon-12 atom.

2. An element with atomic mass number of 14 and atomic number 6 has how many neutrons?

a. 6

b. 8

c. 14

d. 20

3. Isotopes of an element have nuclei with

a. the same number of protons, but different numbers of neutrons.

b. the same number of protons, and the same number of neutrons.

c. a different number of protons, and a different number of neutrons.

d. a different number of protons, and the same number of neutrons.

4. If an atom's atomic number is given by Z, its atomic mass by A, and its neutron number

by N, which of the following is correct?

a. N = A + Z

b. N = Z - A

c. N = A - Z

d. None of the above is correct.

5. In a {93/41}Nb nucleus, the number of protons, neutrons, and electrons is

a. 41, 52, 93

b. 41, 52, 52

c. 41, 52, 41

d. 41, 52, 0

6. The binding energy per nucleon

a. increases steadily as we go to heavier elements.

b. decreases steadily as we go to heavier elements.

c. is approximately constant throughout the periodic table, except for very light nuclei.

d. has a maximum near iron in the periodic table.

7. An alpha particle is also known as

a. an electron.

b. a positron.

c. a helium nucleus.

d. a photon.

8. A beta^- particle is also known as

a. an electron.

b. a positron.

c. a helium nucleus.

d. a photon.

9. The existence of the neutrino was postulated in order to explain

a. alpha decay.

b. gamma emission.

c. beta decay.

d. fission.

10. When an alpha particle is emitted from an unstable nucleus, the atomic mass number

of the nucleus

a. increases by 2.

b. decreases by 2.

c. increases by 4.

d. decreases by 4.

e. none of the above.

11. If 4.0X10¹⁸ atoms decay with a half-life of 2.3 years, how many are remaining

after 3.7 years?

a. 2.5X10¹⁸

b. 1.7X10¹⁸

c. 1.3X10¹⁸

d. 1.1X10¹⁸

12. A radioactive sample has a half-life of 5.0 min. What fraction of the sample is left

after 20 min?

a. 1/2

b. 1/4

c. 1/8

d. 1/16

13. The half-life of radioactive iodine-137 is 8.0 days. How many iodine nuclei are

necessary to produce an activity of 1.0 micro-Ci?

a. 2.9X10⁹

b. 4.6X10⁹

c. 3.7X10¹⁰

d. 7.6X10¹²

14. What happens to the half-life of a radioactive substance as it decays?

a. It remains constant.

b. It increases.

c. It decreases.

d. It could do any of these.

15. The mass of {90/38}Sr is 89.907737 u and the mass of the atom its beta decays to is
89.907151 u. What is the energy released in the decay?

a. 1.2 MeV

b. 112 keV

c. 0.546 MeV

d. 1.8 MeV

Answers:

1. d

2. b

3. a

4. c

5. d

6. d

7. c

8. a

9. c

10. d

11. c

12. d

13. c

14. a

15. c