Honors Chem
Nuclear Chemistry Review
1.
Name ______________________________________
# _______
What makes atoms radioactive?
An unstable nucleus possible due to a large size or a large difference between numbers of protons and neutrons
2.
What makes nuclear reactions different from chemical reactions?
In nuclear reactions, the nucleus is changed to make it more stable. In chemical reactions, the nucleus remains unchanged.
3.
What is it called when an element is changed to a new element during a nuclear reaction?
4.
An isotope of Cerium had a mass of 145.6688g initially and after decay the mass was measured at 145.6107g. How much
energy was produced through this decay process?
E = mc2
m = 145.6688 g – 145.6107 g = 0.0581 g
E=?
0.0581 g
1
x
1 kg
1 x 103 g
=
E = 5.23 x 1012 J
Calculate the energy produced in kilojoules when an isotope lost 0.0245g of mass during its decay period.
E = mc2
E=?
0.0245 g
1
x
1 kg
1 x 103 g
m = 0.0245 g
=
c = 3.00 x 108 m/s
2.45 x 10-5 kg
E = 2.45 x 10-5 kg (3.00 x 108 m/s)2
2.21 x 1012 J
1
6.
c = 3.00 x 108 m/s
5.81 x 10-5 kg
E = 5.81 x 10-5 kg (3.00 x 108 m/s)2
5.
transmutation
x
1 kJ
1 x 103 J
=
E = 2.21 x 1012 J
2.21 x 109 kJ
What is ionizing radiation, and why is it a health concern?
Ionizing radiation is radiation that is powerful enough to knock electrons out of atoms. It is a health concern because it can
damage molecules, including DNA.
7.
How does the band of stability change as the atomic number increases?
When the atomic number is low, atoms are stable with roughly a 1:1 ratio of protons to neutrons. As the atomic number
increases, the band shifts and atoms a higher ratio of neutrons to protons to be stable.
8.
Fill in the table below. (some cells may be blank)
Type of Radiation
Particle Symbol
Side of Equation
(reactant or product)
Alpha decay
4 α
2
Product
Beta decay
0 β
-1
Product
Electron capture
0 e
-1
Reactant
0
1
e
Product
0 γ
0
Product
Positron emission
Gamma ray
Alternate Names
Beta negative emission
Beta positive emission
9.
Show all work for each step(s) in the following nuclear reactions.
a)
Polonium – 210 decays by 2 successive alpha particle emissions.
210 Po
84
 42α + 20682Pb
206 Pb
82
 42α + 20280Hg
b) Copper – 59 decays by electron capture and then by alpha particle emission.
+ 0-1e  5928Ni
59 Cu
29
59 Ni
28
c)
 42α + 5526Fe
Lead – 212 decays by beta negative emission, then by alpha particle emission, and then by positron emission.
212 Pb
82
 0-1 + 21283Bi
212 Bi
83
 42α + 20881Tl
208 Tl
81
 01e + 20880Hg
d) The product of two successive alpha particle emissions is Radium – 235.
243 U
92
 42α + 23990Th
239 Th
90
 42α + 23588Ra
10. Define the following terms and give examples of each process:
a)
Nuclear Fission – The splitting of a larges nucleus into smaller nuclei. It is used to fuel nuclear bombs and power
plants.
b) Nuclear Fusion- The combining of smaller nuclei to form a larger nucleus. It is used to fuel hydrogen bombs and
stars.
11. A sample contains 0.5 g of radioactive material after 10 half-lives. What was the mass of the original amount of radioactive
material?
0.5g  1g  2g  4g  8g  16g  32g  64g  128g  256g  512g
12. 400 g of a radioactive material decayed over 20 h. What fraction of the original sample is left if the half-life for the material
is 5 h?
20 h / 5h = 4 half-lives
400g  200g  100g  50g  25g
1 
½ 
¼  1/8  1/16
13. Why are nuclides with short half -lives always used for medical procedures?
Nuclides with short half-lives will have most of the sample decay in a short period of time. This limits the patient’s exposure
to radioactivity.
14. Why is C – 14 dating not an accurate way to determine the age of an object older than 50,000 yrs. old?
The half-life for C-14 is not quite 6,000 years. At 50,000 years, the sample would have very little C-14 left to measure.
15. An isotope with an original mass of 22.0g was allowed to decay for 7.7 days. What is the amount remaining if the half life is
3.3 days? (This is bonus level work.)
A = A0ekt
A= 11.0g
A0= 22.0g
11.0g = 22.0g ek( 3.3 days)
0.5 = ek( 3.3 days)
ln 0.5 = k (3.3 days)
A = A0ekt
A= ?
A0= 22.0 g
-1 (7.7 days)
A = (22.0 g) e-0.2100446 d
k=?
t= 3.3 days
k= -0.2100446 d-1
k = -0.2100446 d-1
A = 4.37 g
t= 7.7 days