Nuclear Reactions
Chapter 10
Standards
• SPS3. Students will distinguish the characteristics
and components of radioactivity
• SPS3a. Differentiate among alpha and beta
particles and gamma radiation.
• SPS3b. Differentiate between fission and
fusion.
• SPS3c. Explain the process half-life as related to
radioactive decay.
• SPS3d. Describe nuclear energy, its practical
application as an alternative energy source,
and its potential problems.
Nuclear Radiation
Radioactive Decay: unstable isotopes emit
particles and release energy to become stable
isotopes.
• after radioactive decay, the element changes
into a different isotope of the same element
or into an entirely different element.
Radiation
Nuclear Radiation: particles and energy
released from the nucleus during radioactive
decay.
Types of Radiation
• Alpha ()
-protons and neutrons
• Beta-minus (-)
-electrons and positrons
• Gamma ()
-high-energy photons
4
2
He
2+
paper
0
-1
1-
lead
e
0
concrete
Types of Nuclear Radiation (pg 238)
Radiation
Type
Alpha
particle
Symbol
What is it? Mass (kg)
2 protons
and 2
neutrons
6.646x10-27
Charge
Travel depth
through
materials
+2
Least far due
to massive
size
-1, (+1)
Farther than
alpha, but
still not far
Beta particle
Fast-moving
electrons or 9.109x10-31
positrons
Gamma ray
Form of
electromagnetic
energy
None
0
Through
clothes; Can
cause harm
Neutron
A neutron
leaving the
nucleus
1.675x10-27
0
Penetrate
the farthest
Nuclear Decay
• Anytime an unstable nucleus emits alpha or
beta particles, the number of protons and
neutrons changes.
• Alpha decay: atomic mass and number
change
• Beta decay: atomic number changes
• Gamma decay: energy of the nucleus is lower,
but no change in atomic number or mass
Nuclear Decay
• Why nuclide (nucleus of an isotope) decay…
to obtain a stable ratio of neutrons to protons
39
19
40
19
K
Stable
K
Unstable
(radioactive)
Alpha Decay
226
88
Ra
222
86
4
2
Rn + He
226 = 222 + 4
88 = 86 + 2
(atomic mass & atomic
number change)
Beta Decay Equations
14
6
C
14
7
C +
0
-1
e
14 = 14 + 0
6 = 7 + (-1)
(atomic mass stays the same;
atomic number changes by 1)
Actinium-217 decays by releasing an alpha
particle. Write the equation for this decay
process and determine which element is formed.
227
89 Ac
+
X
Z
A
4
2
He
Complete the following radioactive-decay
equation. Identify the isotope X. Indicate
whether alpha or beta decay takes place.
63
28
Ni
A
Z
X + e
0
-1
Radioactive Decay Rates
• Half-life: time in which half of a radioactive
substance decays; measure of how quickly a
substance decays.
-Iodine-131: used by doctors to diagnose
medical problems
-Potassium-40: used by geologists to predict
the age of rocks
Calculating Half-Life
• Radium-226 has a half-life of 1599 years. How
long will 7/8 of a sample take to decay?
1. Find out how much will be left.
8/8 - 7/8 = 1/8 left over
2. Calculate how many half-lives until only 1/8 is
left.
One half life
Two half lives
Three half lives
1/2
1/4
1/8
3. Calculate how many years it will take for 3 half lives
to occur.
1599 x 3 = 4797 years
1
Nuclear Fission
• Nuclear fission: the process by which a
nucleus splits and neutrons and energy are
released.
• Nuclear chain reaction: a continuous series
of fission reactions (pg 340)
Nuclear Fusion
• Nuclear fusion: when 2 light nuclei combine
to form a heavier nuclei
-Hydrogen is turned into Helium on the sun.
(pg 342)
Radiation on Earth
• All around you.
• Background radiation: arises naturally from
the sun, soil, rocks, and plants
• You are exposed to more radiation in the
mountains than at sea level
Beneficial Uses of Radiation
• Smoke detectors release alpha particles
• Radiation is used in x rays, MRIs, CT scans, PET
scans, and ultrasounds
• Radiation therapy is used to treat cancer
• Used in agriculture to track the flow of water
Nuclear Radiation Risks
• High levels of radiation exposure can cause
radiation sickness
• High concentrations of radon gas can cause
cancer
Nuclear Power
Advantages
Disadvantages
Does not produce greenhouse
gases
Radioactive products must be
handled and stored carefully so
they do not escape.
Much more energy available in
Expensive to build due to many
uranium reserves than gas and
safety regulations.
coal.
Waste must be stored in areas
away from people, homes,
water, earthquakes.