Question 1

During $\beta ^ { + }$decay

Accepted Answer

A)  a proton is ejected from the nucleus. 
B)  a neutron is ejected from the nucleus. 
C)  the number of nucleons decreases. 
D)  a neutron is transformed to a proton. 
E)  a proton is transformed to a neutron. 
A)  a proton is ejected from the nucleus. 
B)  a neutron is ejected from the nucleus. 
C)  the number of nucleons decreases. 
D)  a neutron is transformed to a proton. 
E)  a proton is transformed to a neutron.

Question 2

Fermium-253 has a half-life of $3.00$ days. A sample of fermium has $3.88 \times 10 ^ { 6 }$ nuclei. What is the initial activity of this sample?

Accepted Answer

A)  $10.4 \mathrm { kBq }$ 
B)  $12.9 \mathrm {~Bq}$ 
C)  $10.4 \mathrm {~Bq}$ 
D)  $12.9 \mathrm { kBq }$ 
A)  $10.4 \mathrm { kBq }$ 
B)  $12.9 \mathrm {~Bq}$ 
C)  $10.4 \mathrm {~Bq}$ 
D)  $12.9 \mathrm { kBq }$

Question 3

How long will it take a 4.50-kBq sample of material to reach an activity level of $0.140 \mathrm { kBq }$ if the half-life of the sample is 435 years?

Accepted Answer

A)  3245 years 
B)  1993 years 
C)  2178 years 
D)  14,478 years 
A)  3245 years 
B)  1993 years 
C)  2178 years 
D)  14,478 years

Question 4

$$\text { Polonium-215, } \begin{array} { c } 
215 \
84
\end{array} \mathrm { Po } , \text { undergoes alpha decay with a half-life of } 1.8 \mathrm {~ms} .$$ (a) What percent of the original polonium-215 is left after 0.010 s?
(b) How many protons and neutrons does the daughter nucleus contain?

Accepted Answer

(a) 2.1% (

Question 5

To a reasonable approximation, the density of a nucleus

Accepted Answer

A)  is independent of the mass number. 
B)  varies unpredictably for different values of $Z$. 
C)  is smaller for large-Z nuclei. 
D)  is qreater for large- $Z$ nuclei. 
A)  is independent of the mass number. 
B)  varies unpredictably for different values of $Z$. 
C)  is smaller for large-Z nuclei. 
D)  is qreater for large- $Z$ nuclei.

Question 6

A radioactive substance with a half-life of 3.0 days has an initial activity of 2400 Bq. What is its activity after 6.0 days?

Accepted Answer

A)  300 Bq 
B)  1800 Bq 
C)  600 Bq 
D)  1200 Bq 
E)  150 Bq 
A)  300 Bq 
B)  1800 Bq 
C)  600 Bq 
D)  1200 Bq 
E)  150 Bq

Question 7

A sample containing $4.0 \times 10 ^ { 18 }$ atoms of a radioactive isotope decays with a half-life of $2.3$ years. How many undecayed atoms are left after $3.7$ years?

Accepted Answer

A)  $1.7 \times 10 ^ { 18 }$ 
B)  $1.3 \times 10 ^ { 18 }$ 
C)  $2.5 \times 10 ^ { 18 }$ 
D)  $1.1 \times 10 ^ { 18 }$ 
A)  $1.7 \times 10 ^ { 18 }$ 
B)  $1.3 \times 10 ^ { 18 }$ 
C)  $2.5 \times 10 ^ { 18 }$ 
D)  $1.1 \times 10 ^ { 18 }$

Question 8

The mean life (time constant) of radon-222 is $5.526 \mathrm {~d}$. If a sample of radon initially contains $6.00 \times$ $10 ^ { 8 }$ radon atoms, how many of them are left after $10.0 \mathrm {~d}$ ?

Accepted Answer

A)  $8.34 \times 10 ^ { 8 }$ 
B)  $7.29 \times 10 ^ { 8 }$ 
C)  $9.82 \times 10 ^ { 7 }$ 
D)  $7.67 \times 10 ^ { 7 }$ 
E)  $8.56 \times 10 ^ { 8 }$ 
A)  $8.34 \times 10 ^ { 8 }$ 
B)  $7.29 \times 10 ^ { 8 }$ 
C)  $9.82 \times 10 ^ { 7 }$ 
D)  $7.67 \times 10 ^ { 7 }$ 
E)  $8.56 \times 10 ^ { 8 }$

Question 9

The decay constant of neptunium-239 is $0.2975 \mathrm {~d}^{ - 1}$. What are its (a) half-life and (b) mean life?

Accepted Answer

(a) 2.330

Question 10

What are the mass number, the atomic number, and neutron number for each of the following particles?
(a) proton
(b) neutron
(c) alpha particle

Accepted Answer

The answer of What are the mass number, the atomic...

Question 11

An yttrium isotope has 39 protons and 50 neutrons in its nucleus. Which one of the following symbols accurately represents this isotope?

Accepted Answer

A)  ${ } _ { 39 } ^ { 50 } \mathrm { Y }$ 
B)  ${ } _ { 50 } ^ { 89 } \mathrm { Y }$ 
C)  ${ } _ { 50 } ^ { 39 } \mathrm { Y }$ 
D)  ${ } _ { 89 } ^ { 39 } \mathrm { Y }$ 
E)  ${ } _ { 39 } ^ { 89 } \mathrm { Y }$ 
A)  ${ } _ { 39 } ^ { 50 } \mathrm { Y }$ 
B)  ${ } _ { 50 } ^ { 89 } \mathrm { Y }$ 
C)  ${ } _ { 50 } ^ { 39 } \mathrm { Y }$ 
D)  ${ } _ { 89 } ^ { 39 } \mathrm { Y }$ 
E)  ${ } _ { 39 } ^ { 89 } \mathrm { Y }$

Question 12

In positron decay, the number of protons in the nucleus is

Accepted Answer

A)  decreased by $1 .$ 
B)  increased by $2 .$ 
C)  increased by $1 .$ 
D)  decreased by 2 . 
E)  remains unchanged. 
A)  decreased by $1 .$ 
B)  increased by $2 .$ 
C)  increased by $1 .$ 
D)  decreased by 2 . 
E)  remains unchanged.

Question 13

The mass number of an atom is equal to the number of what particles in the nucleus?

Accepted Answer

A)  positrons. 
B)  electrons 
C)  nucleons 
D)  protons 
E)  neutrons 
A)  positrons. 
B)  electrons 
C)  nucleons 
D)  protons 
E)  neutrons

Exam 30: Nuclear Physics and Radioactivity

During β+\beta ^ { + }β+ decay

Fermium-253 has a half-life of 3.003.003.00 days. A sample of fermium has 3.88×1063.88 \times 10 ^ { 6 }3.88×106 nuclei. What is the initial activity of this sample?

How long will it take a 4.50-kBq sample of material to reach an activity level of 0.140kBq0.140 \mathrm { kBq }0.140kBq if the half-life of the sample is 435 years?

start text Poloniumnegative215comma end text 215 84 Pocomma start text undergoes alpha decay with a halfnegativelife of end text 1point8 mspoint (a) What percent of the original polonium-215 is left after 0.010 s? (b) How many protons and neutrons does the daughter nucleus contain?

To a reasonable approximation, the density of a nucleus

A radioactive substance with a half-life of 3.0 days has an initial activity of 2400 Bq. What is its activity after 6.0 days?

A sample containing 4.0×10184.0 \times 10 ^ { 18 }4.0×1018 atoms of a radioactive isotope decays with a half-life of 2.32.32.3 years. How many undecayed atoms are left after 3.73.73.7 years?

The mean life (time constant) of radon-222 is 5.526 d5.526 \mathrm {~d}5.526 d . If a sample of radon initially contains 6.00×6.00 \times6.00× 10810 ^ { 8 }108 radon atoms, how many of them are left after 10.0 d10.0 \mathrm {~d}10.0 d ?

The decay constant of neptunium-239 is 0.2975 d−10.2975 \mathrm {~d}^{ - 1}0.2975 d−1 . What are its (a) half-life and (b) mean life?

What are the mass number, the atomic number, and neutron number for each of the following particles? (a) proton (b) neutron (c) alpha particle

An yttrium isotope has 39 protons and 50 neutrons in its nucleus. Which one of the following symbols accurately represents this isotope?

In positron decay, the number of protons in the nucleus is

The mass number of an atom is equal to the number of what particles in the nucleus?

Introduction, Measurement, Estimating

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Filters

During $\beta ^ { + }$ decay

Fermium-253 has a half-life of $3.00$ days. A sample of fermium has $3.88 \times 10 ^ { 6 }$ nuclei. What is the initial activity of this sample?

How long will it take a 4.50-kBq sample of material to reach an activity level of $0.140 \mathrm { kBq }$ if the half-life of the sample is 435 years?

A sample containing $4.0 \times 10 ^ { 18 }$ atoms of a radioactive isotope decays with a half-life of $2.3$ years. How many undecayed atoms are left after $3.7$ years?

The mean life (time constant) of radon-222 is $5.526 \mathrm {~d}$ . If a sample of radon initially contains $6.00 \times$ $10 ^ { 8 }$ radon atoms, how many of them are left after $10.0 \mathrm {~d}$ ?

The decay constant of neptunium-239 is $0.2975 \mathrm {~d}^{ - 1}$ . What are its (a) half-life and (b) mean life?