### PS Unit 10 Nuclear Reactions

```Nuclear Reactions
Chapter 10
Standards
• SPS3. Students will distinguish the characteristics
• SPS3a. Differentiate among alpha and beta
• SPS3b. Differentiate between fission and
fusion.
• SPS3c. Explain the process half-life as related to
• SPS3d. Describe nuclear energy, its practical
application as an alternative energy source,
and its potential problems.
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.
released from the nucleus during radioactive
decay.
• Alpha ()
-protons and neutrons
• Beta-minus (-)
-electrons and positrons
• Gamma ()
-high-energy photons
4
2
He
2+
paper
0
-1
1-
e
0
concrete
Types of Nuclear Radiation (pg 238)
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
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
equation. Identify the isotope X. Indicate
whether alpha or beta decay takes place.
63
28
Ni
A
Z
X + e
0
-1
• 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)
• 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
• 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
• High levels of radiation exposure can cause
• High concentrations of radon gas can cause
cancer
Nuclear Power
Does not produce greenhouse
gases