Name: _____________________________________________________________
Chapter 25: Nuclear Chemistry
RADIOACTIVITY
NUCLEAR DECAY - a process by which unstable nuclei emit particles of ionizing radiation,
including alpha particles, beta particles and gamma rays.
The bottom
number (atomic
numbers) on the
left of the arrow
must equal the
sum of the bottom
numbers (atomic
numbers) on the
right of the arrow!
Types of Natural Radioactivity:
ALPHA DECAY https://www.youtube.com/watch?v=JwrehvNOSz4
1.
http://youtu.be/CwExbnOzc4o
alpha particle:
α
4
or 2𝐻𝑒
The top number
(mass numbers)
on the left of the
arrow must equal
the sum of the top
numbers (mass
numbers) on the
right of the arrow!
EXAMPLES: Alpha decay is when the radioactive element spits out an alpha particle.
238
92𝑈

234
90𝑇ℎ
(alpha decay – spits out an alpha particle)

238
92𝑈
4
 ___________ + ____ 2𝐻𝑒 __
234
4
(alpha decay with gamma radiation) __ 90𝑇ℎ__  ___________ + __ 2𝐻𝑒 ___ +
0
0

alpha decay: When an alpha particle is emitted the atomic number goes down by ____ and the mass
number goes down by ____. An alpha particle is made up of ___ protons and ___
neutrons
The bottom
number (atomic
numbers) on the
left of the arrow
must equal the
sum of the bottom
numbers (atomic
numbers) on the
right of the arrow!
BETA DECAY -- http://youtu.be/uqAA_D9Mi_I
Beta Particle:
𝑜
−1𝑒
or
𝑜
−1𝛽
EXAMPLES:
14
6𝐶

24
10𝑁𝑒

(beta decay)
(beta decay with gamma radiation)
14
6𝐶
The top number
(mass numbers)
on the left of the
arrow must equal
the sum of the top
numbers (mass
numbers) on the
right of the arrow!
𝑜
 ___________ + __ −1𝑒 __
24
𝑜
___ 10𝑁𝑒 __  ___________ + __ −1𝑒 __ +
Beta decay: When a beta particle is emitted the atomic number goes up by ____ and the mass
number doesn’t change. A beta particle is basically an electron.
1

3. What is gamma radiation? And, why is it so harmful? because gamma radiation has high ____________
and high ______________________ so it is very penetrating to the cells of living things.
Comparing Alpha, Beta and Gamma Radiation
Alpha radiation has a positive charge (because of the two protons). It is the least penetrating and
therefore the least dangerous.
Beta radiation has a negative charge. It is “in the middle” in terms of penetrating power.
Gamma radiation is energy. It has no mass. It is the most harmful since it is the most penetrating of all
three natural emissions.
PRACTICE:
60
27𝐶𝑜
2
Write equations for the following nuclear reactions:

(alpha decay with gamma radiation ) _________  ___________ + __________ +
131
53𝐼

(beta decay )
40
19𝐾

(positron emission )

__________  ___________ + __________
__________  ___________ + ____________
109
46𝑃𝑑

(alpha decay )
__________  ___________ + __________ +

269
110𝐷𝑠

(beta decay with gamma radiation)
__________  ___________ + __________ +

PRACTICE: Nuclear Reactions
0
1. 42
19𝐾  −1𝑒 + ___________________
4
2. 239
94𝑃𝑢 2𝐻𝑒 + __________________
231
3. 235
92𝑈 ________________ + 90𝑇ℎ
0
4. __________________  40
20𝐶𝑎 + −1𝛽
5. 147𝑁 + 10𝑛 ______________ + 11𝐻
0
6. _________________ + 10𝑛 239
93𝑁𝑝 + −1𝛽
1
7. 113
48𝐶𝑑 + 0𝑛 __________________ + 
8. 21𝐻 + _______________  42𝐻𝑒 + 10𝑛
4
1
9. 239
92𝑈 + 2𝐻𝑒 _______________ + 0𝑛
10. 11𝐻 + 31𝐻 ___________________
11. 49𝐵𝑒 + 11𝐻 _______________ + 42𝛼
12. 63𝐿𝑖 + 10𝑛 42𝐻𝑒 + _________________
54
2
13. 56
26𝐹𝑒 + 1𝐻  _____________ + 25𝑀𝑛
54
1
14. 209
83𝐵𝑖 + 24𝐶𝑟  0𝑛 + ____________________
3
Half-Life - http://youtu.be/WAsmY4ocWSA
half life:
PROBLEMS: Use the example in number 1 to solve the rest.
1. The half life of Potassium-40 is 1.3billion years. How much of a 4.00g sample of Potassium-40 remains
after 5.2billion years?
Cut the mass in half for each half life that passes
4.00g  2.00g  1.00g  0.5g  0.25g
Total time = # half life cycles
Half life
()
5.2 billion = 4
1.3 billion
2. The half life of francium is 22 minutes. How much of a 2000g sample of francium remains after 66
minutes? Hint: how many half-lives have happened?
3. Find the half-life of an isotope if 50.0g of the isotope decays to 6.25g in 3600 years. Hint: how many
half-lives have happened
Cut the mass in half for each half life that passes
3600 years = 1200 years is the half life
3
50.0g  25.0g  12.5g  6.25g (so 3 half lives passed)
4. A sample of francium originally has a mass of 40.0g. When the scientist returns from lunch, the mass of
francium in the sample has decreased to 5.0g. If the half-life of francium is 22 minutes, how long was
the scientist’s lunch break? Hint: how many half-lives have happened
4
Practice Half-Life
1. How much of a 100.0g sample of 198Au is left after 8.10 days if its half life is 2.70 days?
2. A 50.0g sample of 16N decays to 12.5g in 14.4 seconds. What is its half life?
3. What is the half life of 99Tc if a 500g sample decays to 62.5g in 639,000 years?
4. The half life of 232Th is 1.4 x 1010 years. If there are 25.0g of the sample left after 2.8 x 1010 years, how
many grams were in the original sample?
5. The half life of 42K is 12.4 hours. How much of a 750g sample is left after 62.0 hours?
5
OTHER NUCLEAR REACTIONS: SKIP this page FOR NOW
1. POSITRON EMISSION: http://youtu.be/bjuZSvZukAw
𝑜
+1𝑒
EXAMPLES:
8
3𝐵

(positron emission )
__________  ___________ + __________
15
8𝑂

(positron emission)
__________  ___________ + __________
2. BETA CAPTURE (also known as electron capture): http://youtu.be/sg_XoUDsP08
.
Beta Particle:
𝑜
−1𝑒
or
𝑜
−1𝛽
EXAMPLES:
6
204
84𝑃𝑜
(beta capture with x rays )
188
76𝑂𝑠
(beta capture with x rays )
__________ + ___________  __________ + x-rays
__________ + ___________  __________ + x-rays
TRANSMUTATION REACTIONS:
FUSION: joining together of nuclei; produces an uncontrollable amount of energy
STEP 1:
𝟑
+ 𝟏𝑯
𝟐
𝟏𝑯
𝟓
𝟐𝑯𝒆

STEP 2:
𝟓
𝟐𝑯𝒆

𝟒
𝟐𝑯𝒆
+
𝟏
𝟎𝒏
+ energy (SUNLIGHT)
FISSION: splitting of nuclei
STEP 1:
𝟏
𝟎𝒏
+
𝟐𝟑𝟓
𝟗𝟐𝑼

𝟐𝟑𝟔
𝟗𝟐𝑼
STEP 2:
𝟐𝟑𝟔
𝟗𝟐𝑼
7

𝟏𝟒𝟒
𝟓𝟔𝑩𝒂
+ 3 𝟏𝟎𝒏 +
𝟖𝟗
𝟑𝟔𝑲𝒓
+ energy
8