Transcript CH_9_2_Nuclear_Equations

Chapter 9 Nuclear Radiation
1
9.2
Nuclear Equations
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
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Balancing Nuclear Equations
2
•
•
In a balanced nuclear equation, particles are emitted from
the nucleus, and
the mass number and atomic number may change
the sum of the mass numbers and the sum of the atomic
numbers are equal for the reactants and the products
Mass number sum:
Atomic number sum:
251 =
251Cf 
98
251
247Cm +
96
98
98
=
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
4He
2
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Guide to Balancing Nuclear Equations
3
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Alpha Decay
4
When a radioactive nucleus emits an alpha particle, a
new nucleus forms with a mass number that is decreased
by 4 and an atomic number that is decreased by 2.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
4 He
2
Equation for Alpha Emission
5
Write an equation for the alpha decay of Rn-222.
Step 1 Write the incomplete nuclear equation.
222Rn  ?  4He
86
2
Step 2 Determine the missing mass number.
222 – 4 = 218
Step 3 Determine the missing atomic number.
86 – 2 = 84
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Equation for Alpha Emission
6
Write an equation for the alpha decay of Rn-222.
Step 4 Determine the symbol of the new nucleus.
84 = Po
Step 5 Complete the nuclear equation.
222Rn  218Po  4He
86
84
2
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Beta Emission
7
A beta particle is an electron emitted from the nucleus
when a neutron in the nucleus breaks down, increasing
the atomic number by 1.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
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Equation for Beta Emission
8
Write an equation for the decay of 42K, a beta emitter.
Step 1 Write the incomplete nuclear equation.
42K  ?  0e
19
1
Step 2 Determine the missing mass number.
42 – 0 = 42
Step 3 Determine the missing atomic number.
19  (1) = 20
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Equation for Beta Emission
9
Write an equation for the decay of 42K, a beta emitter.
Step 4 Determine the symbol of the new nucleus.
20 = Ca
Step 5 Complete the nuclear equation.
42K  42Ca  0e
19
20
1
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
10
Write the nuclear equation for the beta decay of 60Co.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
11
Write the nuclear equation for the beta decay of
Step 1 Write the incomplete nuclear equation.
60Co.
60Co  ?  0e
27
1
Step 2 Determine the missing mass number.
60 – 0 = 60
Step 3 Determine the missing atomic number.
27  (1) = 28
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
12
Write the nuclear equation for the beta decay of
60Co.
Step 4 Determine the symbol of the new nucleus.
28 = Ni
Step 5 Complete the nuclear equation.
60Co  60Ni  0e
27
28
1
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
0e
1
Positron Emission
13
In positron emission,
• a proton is converted to a neutron and a positron.
1 p  1n  0e
1
0
1
• the mass number of the new nucleus is the same, but the
atomic number decreases by 1.
49Mn  49Cr  0e
25
24
1
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Gamma Radiation
0
0
14
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  99Tc  0
43
43
0
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Summary of Types of Radiation
15
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Producing Radioactive Isotopes
16
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
When nonradioactive B-10 is bombarded by an alpha particle, the products
are radioactive N-13 and a neutron.
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Learning Check
17
What radioactive isotope is produced when a neutron
bombards 98Tc, releasing an alpha particle?
98Tc  1n  ?  4He
27
0
2
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
18
What radioactive isotope is produced when a neutron
bombards 98Tc, releasing an alpha particle?
Step 1 Write the incomplete nuclear equation.
98Tc  1n  ?  4He
27
0
2
Step 2 Determine the missing mass number.
98 + 1  4 = 95
Step 3 Determine the missing atomic number.
27  2 = 25
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.
Solution
19
What radioactive isotope is produced when a neutron
bombards 98Tc, releasing an alpha particle?
Step 4 Determine the symbol of the new nucleus.
25 = Mn
Step 5 Complete the nuclear equation.
98Tc  1n  95Mn  4He
27
0
25
2
Chemistry: An Introduction to General, Organic, and Biological Chemistry, Eleventh Edition
Copyright © 2012 by Pearson Education, Inc.