Deck 40: Nuclei

Question 1

Acceptable dimensions of the mass number A are

A) kilograms.
B) joules.
C) either of the first two responses, because $\mathrm { E } = m c ^ { 2 }$
D) neither of the first two responses is correct.

Answer 1

neither of the first two responses is correct.

Question 2

The nuclear radius of ⁶⁴Co is approximately

A) 1.2 fm.
B) 4.8 fm.
C) 6.0 fm.
D) 12 fm.
E) None of the above responses is correct.

Answer 2

12 fm.

Question 3

The nuclear radius of ²⁷Co is approximately

A) 1.2 fm.
B) 3.6 fm.
C) 4.5 fm.
D) 6.0 fm.
E) None of the above responses is correct.

Answer 3

3.6 fm.

Question 4

The density of nuclear matter is of the order of

A) 10³ kg/m³.
B) 10⁷ kg/m³.
C) 10¹⁷ kg/m³.
D) 10⁵⁰ kg/m³.
E) None of the above responses is correct.

Question 5

A valid inference from the fact that the radius of the nucleus is related to the mass number A is that

A) the nuclear force obeys an inverse square law.
B) the number of nucleons per unit volume in atoms is independent of the element.
C) the atomic size increases as the nuclear size increases.
D) the nucleons in a nucleus are separated by distances large compared to their individual sizes.

Question 6

Compared to atomic energies, nuclear energies are

A) a million times larger.
B) a thousand times larger.
C) of about the same magnitude.
D) a thousand times smaller.
E) a million times smaller.

Question 7

All isotones of a given element

A) have the same chemical properties.
B) have the same number of protons.
C) have the same number of nucleons.
D) have the same number of neutrons.
E) All of the above are true.

Question 8

The graphs here show the number of protons as a function of the number of neutrons. Two nuclides that are isotopes could lie on the curve in graph

A)
B)
C)
D)
E)

Question 9

The graphs here show the number of protons as a function of the number of neutrons. Two nuclides that are isotones could lie on the curve in graph

A)
B)
C)
D)
E)

Question 10

In comparison with an electron, a proton has larger

A) mass and size.
B) spin.
C) magnetic moment.
D) All of the previous answers are correct.
E) None of the previous answers is correct.

Question 11

In comparison with an electron, a proton has the same

A) mass and size.
B) spin.
C) magnetic moment.
D) All of the previous answers are correct.
E) None of the previous answers is correct.

Question 12

In a ${ } _ { 56 } ^ { 135 } \mathrm { Ba }$ nucleus, the numbers of protons, neutrons, and electrons are

A) 56, 79, and 135, respectively.
B) 56, 79, and 0, respectively.
C) 79, 56, and 135, respectively.
D) 79, 56, and 0, respectively.
E) None of the previous answers is correct.

Question 13

Of the total nuclear rest-mass energy, the nuclear binding energy amounts to approximately

A) 0.1%.
B) 1.0%.
C) 10%.
D) 50%.
E) 90%.

Question 14

The mass of a typical nucleus is

A) somewhat less than the sum of the masses of its constituents.
B) somewhat more than the sum of the masses of its constituents.
C) equal to the sum of the masses of its constituents.
D) None of the previous responses is a valid generalization.

Question 15

In terms of increasing penetrating ability, the three kinds of rays emitted by radioactive isotopes are

A) $\alpha , \beta , \gamma$
B) $\beta , \gamma , \alpha$
C) $\gamma , \alpha , \beta$
D) $\beta , \alpha , \gamma$
E) All have the same penetrating ability.

Question 16

In terms of charge, the $\alpha , \beta , \gamma$ rays emitted by radioactive isotopes are, respectively

A) positive, neutral, and negative.
B) positive, negative, and neutral.
C) negative, neutral, and positive.
D) negative, positive, and neutral.
E) neutral, negative, and positive.

Question 17

During $\beta ^ { + }$ decay,

A) a neutron is ejected from the nucleus.
B) a neutron is transformed to a proton.
C) a proton is transformed to a neutron.
D) a proton is ejected from the nucleus.
E) None of the above is true.

Question 18

If the parent nucleus has N neutrons and Z protons, after an $\alpha$ decay, the daughter nucleus has respective neutron and proton numbers of

A) N and Z - 1.
B) N and Z + 1.
C) N - 2 and Z - 2.
D) N - 1 and Z - 1.
E) N and Z.

Question 19

If the parent nucleus has N neutrons and Z protons, after the ejection of a positron (anti-electron) in a $\beta$ decay, the daughter nucleus has respective neutron and proton numbers of

A) N - 1 and Z - 1.
B) N - 1 and Z + 1.
C) N and Z - 2.
D) N + 1 and Z + 1.
E) N + 1 and Z - 1.

Question 20

The radioactive decay mode where the daughter and the parent nuclides are the same element is

A) $\alpha$ decay.
B) $\beta$ decay.
C) $\gamma$ decay.
D) None of the previous responses is valid.

Question 21

When ²³⁸U emits an $\alpha$ -particle and two $\gamma$ -rays,

A) ²³⁴U is produced.
B) ²³⁸Th is produced.
C) ²³⁴Th is produced.
D) ²³⁶Th is produced.
E) ²⁴²Pu is produced.

Question 22

Which of the following is most likely to undergo fission?

A) ²H.
B) ⁴He.
C) ³²P.
D) ⁵⁶Fe.
E) ²³⁵U.

Question 23

Which of the following is most likely to release energy when undergoing fusion with other nuclei?

A) ²H.
B) ⁴He.
C) ³²P.
D) ⁵⁶Fe.
E) ²³⁵U.

Question 24

The binding energy per nucleon is greatest for nuclei of

A) small mass.
B) intermediate mass.
C) large mass.
D) More information is needed to work out the answer.

Question 25

In $\beta$ decay it is found that both the direction of the ejected electron (with respect to the recoil direction of the parent nucleus) and the magnitude of the electron's velocity are variable. From these facts, we can infer that another particle (the neutrino, as it turns out) is needed to preserve the conservation of

A) energy.
B) momentum.
C) all of the above.
D) none of the above.

Question 26

The significant forces in determining the structure of nuclei are

A) coulomb and gravitational.
B) gravitational and weak.
C) strong and weak.
D) coulomb and strong.
E) gravitational, coulomb, and strong.

Question 27

The binding energy per nucleon is

A) the same for all atoms.
B) proportional to atomic number.
C) inversely proportional to atomic number.
D) strongly dependent on charge.
E) none of the above.

Question 28

The atomic mass of the deuteron (the nucleus of the deuterium atom), which consists of a proton (mass 1.007825 u) and a neutron (mass 1.007825 u), is 2.014102 u. The binding energy of the deuteron is

A) 2.224 J.
B) 2.224 keV.
C) 2.224 MeV.
D) 3.754 keV.
E) 3.754 MeV.

Question 29

The nucleus with the larger binding energy per nucleon is

A) ²³⁸U.
B) ¹⁹⁷Au.
C) ⁶²Ni.
D) ⁴He.
E) ²H.

Question 30

The half-life of carbon-14 is about 6000 years. If the amount of carbon-14 remaining in a sample is 1/100 of the original amount, the atoms of the sample began decaying about

A) 20,000 years earlier.
B) 40,000 years earlier.
C) 60,000 years earlier.
D) 80,000 years earlier.

Question 31

If the half-life of a material is 45 years, how much will be left after 100 years?

A) less than a quarter.
B) more than a quarter.
C) less than half.
D) more than half.
E) More information is needed to work out the answer.

Question 32

As a radioactive substance decays, its half-life

A) increases.
B) stays the same.
C) decreases.

Question 33

A sample of ¹³¹I (which has a half-life of 8.04 days) has an activity of 5.0 mCi at the time of shipment, and an activity of 4.2 mCi upon receipt in a medical laboratory. The time elapsed between the shipment and the receipt is

A) 6.8 days.
B) 6.4 days.
C) 5.0 days.
D) 2.5 days.
E) 2.0 days.

Question 34

The number of ¹³¹I (half-life of 8.04 days) nuclei necessary to produce an activity of 5.0 mCi is

A) 8.91 * 10¹⁴.
B) 1.85 * 10¹⁴.
C) 3.09 * 10¹².
D) 5.01 * 10⁶.
E) 5.01 * 10³.

Question 35

A 300-g sample of ²¹⁸Po undergoes $\alpha$ decay with a half-life of 3.1 minutes. After 15.5 minutes,

A) 9.38 g of ²¹⁴Pb would be formed.
B) 18.8 g of ²¹⁴Pb would be formed.
C) 120 g of ²¹⁴Pb would be formed.
D) 281 g of ²¹⁴Pb would be formed.
E) 291 g of ²¹⁴Pb would be formed.

Question 36

The radioactivity of a certain radioisotope decreases to one-half in 1.0 hour. Three hours later, its radioactivity, compared with that at the beginning of the first hour, is

A) 1/2.
B) 3/2.
C) 1/4.
D) 1/6.
E) 1/8.

Question 37

If 30 g of substance remain from an original sample of 240 g after 600 days, the half-life of the substance is

A) 50 days.
B) 70 days.
C) 100 days.
D) 200 days.
E) 400 days.

Question 38

A certain radioisotope has a lifetime of 40 days. The time it will take for 3/4 of the originally present nuclei to disintegrate is

A) 17 days.
B) 30 days.
C) 40 days.
D) 63 days.
E) 80 days.

Question 39

If 40 g of substance of half-life 5.0 hours remain from an original sample of 1.28 kg, the time that has passed is

A) 1.0 hour.
B) 20 hours.
C) 25 hours.
D) 80 hours.
E) 160 hours.

Question 40

After 4.5 days, 50 g of substance remain from an original sample having a half-life of 1.5 hours. The original amount of substance was

A) 17 g.
B) 50 g.
C) 150 g.
D) 400 g.
E) 600 g.

Question 41

At a particular time, a radioactive source A has a strength of 1.60 *10¹¹ Bq and a half-life of 8.00 days, and a radioactive source B has a strength of 6.40 *10¹¹ Bq. The two sources have the same strength 30.0 days later. The half-life of source B is

A) 35.7 days.
B) 24.7 days.
C) 17.2 days.
D) 7.53 days.
E) 5.22 days.

Question 42

The graph here shows the number of undecayed nuclei as a function of time for a radioactive element. The half-life of this particular radioisotope is

A) 1.0 s.
B) 2.0 s.
C) 4.0 s.
D) 6.0 s.
E) More information is needed to work out the answer.

Question 43

The graph here shows the number of undecayed nuclei as a function of time for a radioactive element. The number of undecayed nuclei at t = 16 s is

A) 30
B) 23
C) 13
D) 5.6
E) More information is needed to work out the answer.

Question 44

The graphs here show the number of undecayed nuclei as a function of time for a radioactive element. The graphs corresponding to elements having the same half-life are

A) A and B.
B) A and C.
C) A and D.
D) B and C.
E) B and D.

Question 45

The graphs here show the number of undecayed nuclei as a function of time for a radioactive element. The graph corresponding to elements having the smaller decay constant is

A) A
B) B
C) C
D) D
E) E

Question 46

The radioactivity due to ¹⁴C (half-life 5730 years) measured in a piece of a wooden casket from an ancient burial site was found to produce 10 counts per minute from a given sample, whereas the same amount of carbon from a piece of living wood produced 160 counts per minute. The estimated age of the artifact is

A) 358 years.
B) 5,700 years.
C) 22,900 years.
D) 45,800 years.
E) 91,700 years.