By Abi Darin,
Sam Rice, & Becky Schur
The Decay Process
• Radioactive decay
occurs with 3 different
particles:
1. Alpha Particle (α)
2. Beta Particle (β)
3. Gama Ray (γ)
Penetrating Abilities
α
10 cm of lead
β
γ
0.5 cm of lead
paper
The Alpha Particle
α
• When α particles are passed
through an electric field they
are attracted to the negative
side.
• Consist of
nuclei.
4
2
He
helium
4
2
α
The Beta Decay
β
• Attracted to the electrically
positive plane.
• Same electrical charge and
mass of an electron.
0
-1
e
0
-1
β
The Gamma Emission
γ
• Gamma particles are
photons.
• They have no mass and no
charge.
• When a gamma ray is
emitted, it gives off energy,
but affects neither the charge
nor the mass of the products.
0
0
γ
Positron Emission
☺e
• A positron is formed when a
proton splits into a neutron and
another particle
1
1
• 1proton → 0 neutron ++10 positron
• Positrons are essentially positive
electrons or positive beta
particles.
0
0
+1
+1
e β
Useful Terms
• Nuclear Reactions- the natural
change of the isotope of one
element into the isotope of a
different element resulting in
radioactivity. A NR changes the
atomic number and often the
mass number.
• Nucleons (baryons)- protons and
neutrons.
See example on the
next page…
Alpha
Decay:
226
88
Mass Number
Ra
4
2
He +
222
86
Rn
226
4
+
222
88
2
+
86
β
+
239
0
+
239
92
-1
+
93
(protons & neutrons)
Atomic Number
(protons)
Beta
Decay:
Mass Number
239
92
U
0
-1
239
93
Np
(protons & neutrons)
Atomic Number
(protons)
Positron 207
84 Po
Emission:
Mass Number
0
+1
e+
207
83
Bi
207
0
+
207
84
+1
+
83
(protons & neutrons)
Atomic Number
(protons)
More terms…
Radioactive Decay Series- a
sequence of decay reactions
that continue until a stable
nonradioactive isotope is formed.
Step 1:
Step 2:
Step 3:
Step 4:
Th + α
234
0
Pa
91
+-1 β
238
92
234
90
234
92
U+ β
230
4
90 Th + 2 α
U
234
90 Th
234
91 Pa
U
234
92
4
2
0
-1
Did you know…
• All elements beyond Bismuth (Bi) are
unstable meaning they are
radioactive usually occurring in an
alpha particle ejection.
• Beta emission occurs in isotopes that
have too many neutrons to be stable.
• Positron emission or electron capture
occurs when isotopes do not have
enough neutrons to be stable.
• Nuclear Binding Energy- a
measure of force holding the
nucleus together.
• Binding energy per nucleonUsed to compare nuclear
stabilities.
• The greater the binding energy
per nucleon, the greater the
stability of the nucleus.
• All elements are thermodynamically unstable with
respect to iron.
Fission Vs. Fusion
• Heavy nuclei splitting= fission.
• 2 Very Light nuclei join together=
fusion.
•Both release substantial
amounts of energy.
Useful Equations
• A = KN
The activity in
particles per
second
The number of
radioactive nuclei
Decay Konstant
•Xf = Xo e
Amount,
activity, etc.
–kt
Decay Konstant
Time
elapsed
And more…
•τ
ln(2)
=
K
1/2
The half life
Decay Konstant
• E = Δmc2
Energy
The natural
logarithm of 2
Speed of light
Mass Defect
• C= 2.99792458 x 108 m/s
Application:
THE END!
Seriously, the end.
Chemistry is over
in about 2 weeks.
What a long,
strange trip it’s
been.