Transcript Chapter 3 Nuclear Radiation

Chapter 9 Nuclear Radiation
9.2
Nuclear Equations
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
1
Alpha Decay
When a radioactive
nucleus emits an
alpha particle, a new
nucleus forms that has
• a mass number that is
4 less than that of the
initial nucleus.
• an atomic number that
is decreased by 2.
2
Balancing Nuclear Equations
In a balanced nuclear equation, the sum of the mass
numbers and the sum of the atomic numbers for the
nuclei of the reactant and the products must be
equal.
MASS NUMBERS
Total =
251
=
251
251Cf
247Cm +
4He
98
Total =
96
2
98
=
98
ATOMIC NUMBERS
3
Guide to Balancing a Nuclear Equation
4
Equation for Alpha Decay
Write an equation for the alpha decay of 222Rn.
STEP 1 Write the incomplete equation
222Rn
?s + 4He
86
2
STEP 2 Determine the mass number
STEP 3 Determine the atomic number
222 – 4 = 218
86 – 2 =
STEP 4 Determine the symbol of element
84
84 = Po
STEP 5 Complete the equation
222Rn
86
218Po
84
+
4He
2
84
Po
85
At
86
Rn
4He
2
5
Beta Decay
A beta particle
• is an electron
emitted from the
nucleus.
• forms when a
neutron in the
nucleus breaks
down.
1n
0e + 1H
0
-1
1
6
Writing An Equation for a Beta Emitter
STEP 1
Write an equation for the decay of
42Potassium,a beta emitter.
42K
new nucleus + 0e
19
-1
STEP 2
STEP 3
STEP 4
Mass number :
(same)
Atomic number:
19 + 1
Symbol of element 20
STEP 5
42K
19
42Ca
20
+
= 42
= 20
= Ca
0e
-1
0e
-1
19
K
20
Ca
7
Learning Check
Write the nuclear equation for the beta decay of 60Co.
8
Solution
60Co
60Ni
27
28
+ 0e
1
beta particle
9
Positron Emission
In position emission,
• a proton is converted to a neutron and a positron.
1p
1n + 0e
1
0
+1
• the mass number of the new nucleus is the same, but
the atomic number decreases by 1.
49Mn
25
49Cr
24
+
0e
+1
10
Gamma  Radiation
In gamma radiation
• energy is emitted from an unstable nucleus,
indicated by m following the mass number.
• the mass number and the atomic number of the
new nucleus are the same.
99mTc
43
99Tc
43
+ 
11
Summary of Types of Radiation
Copyright © 2005 by Pearson Education, Inc.
Publishing as Benjamin Cummings
12
Summary of Types of Radiation
13
Summary of Changes in Mass and
Atomic Numbers
TABLE 9.4
14
Relative Penetration of Radiation
15
Producing Radioactive Isotopes
Radioactive isotopes are produced
• when a stable nucleus is converted to a radioactive
nucleus by bombarding it with a small particle.
• in a process called transmutation.
16
Learning Check
What radioactive isotope is produced when a
neutron bombards 59Co?
59Co
27
+
1n
0
? +
4He
2
17
Solution
mass numbers
60
=
60
59Co + 1n
56Mn +
4H e
27
0
27
25
2
=
27
atomic numbers
18
Artificial Transmutation
a. Induced Radioactivity
1. Bombarding a normally stable nucleus
with high-energy particles can lead to
transmutation of one element into
another.
b. Transuranic Elements
1. Elements heavier than uranium (Z=92),
the transuranic elements, do not occur
in nature but can be made through
artificial transmutation.
19
Irène and Frédéric Joliot-Curie
Were the 1st to produce a radioactive nuclide through artificial transmutation
Credit: Corbis
20
Transuranic elements in the periodic table
Elements higher than Uranium 92
are transuranic elements
21