Transcript Mass Numbers - Houston ISD

Nuclear Chemistry
•The study of the structure of
atomic nuclei and the changes they
undergo.
Radioactivity and
Radioactive Decay
Today’s Objective
1. Describe why certain nuclei are radioactive.
2. Write nuclear decay equations to depict the
nuclear decay of radioisotopes.
Isotopes - Atoms which possess the same
atomic number, but different mass
numbers. (Same number of protons,
different number of neutrons)
1
2
3
1
1
1
Complete the Table Below
Name
Protons
Neutrons
Atomic
Number
Mass
Number
6
8
6
14
K
19
22
19
41
Pb
82
124
82
206
Symbol
Carbon-14
14
6
Potassium-41
41
19
Lead-206
206
82
C
Radioactivity
 What is radioactivity?
 Radioactivity occurs when an unstable nucleus
spontaneously emits fragments of the nucleus
and/or energy.
Unstable Nucleus = Radioactive
 Why are only some isotopes radioactive?
 The ratio of protons to neutrons in the nucleus
determines whether or not a nucleus is
radioactive.
Radioactive Isotopes
Stable Isotopes -Atoms that do not
release protons or neutrons from the
nucleus and ARE NOT
RADIOACTIVE.
Unstable Isotopes - Atoms that
spontaneously release protons and
neutrons from its nucleus. These
isotopes ARE RADIOACTIVE.
Band of Stability
 The region on a graph
which indicates all
stable nuclei when the
number of neutrons are
compared to the
number of protons for
all stable nuclei
 Developed a formula to
describe how some of the
mass can be converted into energy.
 Shown by a very famous equation!
E=mc2
Energy
Mass
When matters is turned into
energy, large amounts of energy are released!
Speed of light
Depicting Nuclear Reaction
For nuclear reactions,
 the sum of the mass numbers (top numbers) and
 the sum of the atomic numbers (bottom number)
must be the same on both sides.
Mass Numbers:
9 + 4 = 12 + 1
13 = 13 
Atomic Numbers:
4+2= 6+0
6 = 6 
Finding the Missing Nucleus
Th He  ?
234
90
4
2
Mass Numbers
234 = 4 + ?
? = 230
Atomic Numbers
90 = 2 + ?
? = 88
230
88
Ra
Finding the Missing Nucleus
C  e X
14
6
0
1
A
Z
Mass Numbers
14 = 0 + A
A = 14
Atomic Numbers
6 = -1 + Z
Z = 7
14
7
N
Finding the Missing Nucleus
3 H  Be  X  He
1
1
Mass Numbers
Atomic Numbers
9
4
A
Z
(3 x 1) + 9 = A + 4
3 + 9 = A + 4
12 = A + 4
A = 8
(3 x 1) + 4 = Z + 2
3 + 4 = Z + 2
7 = Z + 2
Z = 5
4
2
8
5
B
Examples of Transmutation Reactions
C  e N
Th He  Ra
234
90
4
2
14
6
230
88
0
1
14
7
3 H  Be B He
1
1
9
4
8
5
4
2
These are all transmutation reactions because
the elements on the left side are changed to
produce a different element on the right side.
Emissions from Radioisotopes
Type of
Particle
Emitted
Description
Alpha
A Helium
Nucleus
4
2
Beta
A Fast Moving
Electron
0
1
Gamma
Electromagnetic
Radiation
Neutron
A neutron
Symbol
Mass
Charge
Why is it
Emitted?
He or 24
4 amu
+2
Nucleus is
too large.
e or 
1
amu
1840
-1
Too many
neutrons
0 amu
0
Too much
energy
1
0
0
1
0
0

1
◦n
Nucleus to
heavy
A radioisotope is a nucleus that is radioactive or unstable.
© 2003 John Wiley and Sons Publishers
Figure 4.4: The components of α rays, β rays, and γ rays.
Radioactivity and
Radioactive Decay
Today’s Objective
1. Write nuclear decay equations to depict the
nuclear decay of radioisotopes.
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
alpha decay of uranium-238.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
U  He 
238
92
4
2
234
90
Th
Mass Number:
238 = 4 + ?
? = 234
Atomic Number:
92 = 2 + ?
? = 90
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
beta decay of iodine-131.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
I  e
131
53
0
1
131
54
Xe
Mass Number:
131 = 0 + ?
? = 131
Atomic Number:
53 = -1 + ?
? = 54
Writing Nuclear Decay Equations
Write the nuclear decay equation the
emission of a gamma ray from carbon-14.
Start your decay equation by writing the symbol
Write the
for the
typean arrow.
for this nucleus
andsymbol
then follow
it with
of decay.
C   C
14
6
0
0
14
6
Mass Number:
14 = 0 + ?
? = 14
Atomic Number:
6=0+?
?=6
Examples of Transmutation Reactions
C  e N
Th He  Ra
234
90
4
2
14
6
230
88
0
1
14
7
3 H  Be B He
1
1
9
4
8
5
4
2
These are all transmutation reactions because
the elements on the left side are changed to
produce a different element on the right side.
Decay Series for Uranium-238
This diagram
shows the steps
that an isotope
of uranium takes
to reach a
stable isotope,
lead-206.
A Closer Look at the Decay Series
Write a nuclear decay equation for what occurs to
uranium-234 according to this decay series.
U  Th He
234
92
230
90
4
2
A Closer Look at the Decay Series
Write a nuclear decay equation for what we occur to
lead-210 according to this decay series.
210
82
Pb 
210
83
Bi  e
0
1
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
alpha decay of uranium-238.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
U  He 
238
92
4
2
234
90
Th
Mass Number:
238 = 4 + ?
? = 234
Atomic Number:
92 = 2 + ?
? = 90
Writing Nuclear Decay Equations
Write the nuclear decay equation for the
beta decay of iodine-131.
Start your
decay equation
by writing the symbol
Write
the symbol
for the type
for this nucleus
and then follow it with an arrow.
of decay.
I  e
131
53
0
1
131
54
Xe
Mass Number:
131 = 0 + ?
? = 131
Atomic Number:
53 = -1 + ?
? = 54
Writing Nuclear Decay Equations
Write the nuclear decay equation the
emission of a gamma ray from carbon-14.
Start your decay equation by writing the symbol
Write the
for the
typean arrow.
for this nucleus
andsymbol
then follow
it with
of decay.
C   C
14
6
0
0
14
6
Mass Number:
14 = 0 + ?
? = 14
Atomic Number:
6=0+?
?=6
Two Types of Nuclear Reactions:
Fission and Fusion
Today’s Objective
Compare and contrast fission and fusion.
Type of
Reaction
Fission
Fusion
Fission versus Fusion
Definition
• Involves the splitting of
a nucleus into two
smaller nuclei
• Often started when a
nucleus is bombarded by
a neutron
• Involves two smaller
nuclei joining together to
create a larger nucleus
Picture or Image
Fission versus Fusion
Fission
Fusion
Splitting of a Nucleus
Releases smaller
amounts of energy
Controllable at
Regular Temperatures
Combining Nuclei
Both
Transmutation
Reactions
Releases larger
amounts of energy
Generally Requires Very
High Temperatures
Produces smaller quantities
More Efficient
of nuclear waste
than Coal or Oil
Examples include the
Examples include
sun, stars, and the
nuclear power plants
hydrogen bomb
and the atom bomb
Produces larger quantities
of nuclear waste
A transmutation reaction is a nuclear reaction that produces a new or
different atom than was originally present.
Fission
produces
a chain
reaction
 Scientists cannot yet find a safe, and manageable method to
harness the energy of nuclear fusion.
 “cold fusion” would occur at temperatures and pressures that
could be controlled (but we haven’t figured out how to get it to
happen)
Radiation Exposure and Half-Life
Today’s Objective
• Discuss how we protect ourselves from radiation
and use nuclear chemistry.
• Determine the meaning of a half-life.
• Current uses of Nuclear reactions
Protecting Ourselves from
Radioactive Particles
© 2003 John Wiley and Sons Publishers
Figure 4.2: The penetrating power of radiation.
Current Nuclear Reactors
Current Nuclear Reactors
Inside a Nuclear Reactor
Applications
Medicine




Chemotherapy
Power pacemakers
Diagnostic tracers
Agriculture



Irradiate food
Pesticide
Energy



Fission
Fusion
© 2003 John Wiley and Sons Publishers
Courtesy Robert Maass/Corbis Images
X-ray examination of luggage at a security station.
Food Irradiation
•Food can be irradiated with  rays from
60Co or 137Cs.
•Irradiated milk has a shelf life of 3 mo.
without refrigeration.
•USDA has approved irradiation of meats
and eggs.
© 2003 John Wiley and Sons Publishers
Courtesy Custom Medical
Stock Photo
An image of a thyroid gland obtained through the use of radioactive iodine.
© 2003 John Wiley and Sons Publishers
Courtesy CNRI/Phototake
Images of human lungs obtained from a γ-ray scan.
© 2003 John Wiley and Sons Publishers
Courtesy Kelley Culpepper/Transparencies, Inc.
A cancer patient receiving radiation therapy.
© 2003 John Wiley and Sons Publishers
Courtesy Scott Camazine/Photo
Researchers
The world’s first atomic explosion, July 16, 1945 at Alamogordo, New Mexico.
© 2003 John Wiley and Sons Publishers
Courtesy Shigeo Hayashi
Remains of a building after the explosion of the uranium bomb at Hiroshima, August 6, 1945.
© 2003 John Wiley and Sons Publishers
Courtesy David Bartruff/Corbis Images
Cooling towers of a nuclear power plant.
© 2003 John Wiley and Sons Publishers
Courtesy Sipa Press
The nuclear power plant at Chernobyl, after the accident of April 16, 1986.
Challenges of Nuclear Power
»Disposal of waste products
 Hazardous wastes produced by nuclear reactions are
problematic.
 Some waste products, like fuel rods, can be re-used
 Some products are very radioactive, and must be stored away
from living things.
 Most of this waste is buried underground, or stored in concrete
 It takes 20 half-lives (thousands of years) before the material is safe.
© 2003 John Wiley and Sons Publishers
Courtesy Yucca Mountain Project
Construction of a tunnel that will be used for burial of radioactive wastes deep within Yucca Mountain,
Nevada.
© 2003 John Wiley and Sons Publishers
Courtesy Matthew Neal McVay/Stone/Getty
Images
Disposal of radioactive wastes by burial in a shallow pit.
© 2003 John Wiley and Sons Publishers
Courtesy AP/Wide World Photos
Albert Einstein, he discovered the equation that relates mass and energy.