Nuclear Reactions
Alpha, Beta, and Gamma Decay
Objectives :
State what is meant by alpha, beta and gamma decay.
Identify the processes occurring in nuclear reactions
written in symbolic form.
The Atom
The atom consists of two parts:
1. The nucleus which contains:
protons
neutrons
2. Orbiting electrons.
The Atom
•All matter is made up of elements (e.g.
carbon, hydrogen, etc.).
•The smallest part of an element is called an
atom.
•Atom of different elements contain
different numbers of protons.
•The mass of an atom is almost entirely due
to the number of protons and neutrons.
Nuclear Symbol
Mass number
A
X
Z
Atomic number
Element symbol
• Chlorine - 35
Nuclear Symbol
 Hyphen notation: carbon -14
 Nuclear symbol:
Mass #
Atomic #
14
6
C
PEN from nuclear symbol
• Chlorine-37
atomic #:
17
mass #:
37
# of protons:
17
# of electrons:
17
# of neutrons:
20
37
17
Cl
Practice
• Write the nuclear symbol for each isotope below:
 Sodium - 25
 Uranium – 235
 Gold – 197
Practice
• Identify the PEN for each od the previous isotopes
25
11
#p
Na
#e
#n
235
92
U
#p
#e
#n
197
79
Au
#p
#e
#n
There are many types of uranium:
235
U
92
238
U
92
Mass #
Mass #
Atomic #
Atomic #
Number of protons
Number of protons
Number of neutrons
Number of neutrons
There are many types of uranium:
238
235
U
92
U
92
Mass #
235
Mass #
238
Atomic #
92
Atomic #
92
Number of protons
92
Number of protons
92
Number of neutrons
143
Number of neutrons
146
Isotopes have the same number of protons, but different
numbers of neutrons.
Nuclear Reactions
•Most isotopes that occur naturally are
stable.
•Few naturally occurring isotopes & all
man-made isotopes are unstable.
•Unstable isotopes become stable by
releasing different types of particles.
•This process is called radioactive decay
and the elements which undergo this
process are called radioisotopes.
Radioactive Decay
Radioactive decay results in
the emission of either:
• an alpha particle (a),
• a beta particle (b),
• a gamma ray(g).
Alpha Decay
• Is identical to that of a helium nucleus
• Contains two protons and two neutrons
4
2
He
Alpha Decay
A
X
Z
A-4
4
Y
He
+
Z-2
2
unstable atom
alpha particle
more stable atom
Alpha Decay
222
226
Ra
88
Rn
86
4
He
2
Alpha Decay
A
A-4
4
226
222
4
X
Z
Ra
88
Y
+
Z-2
Rn
+
86
He
2
He
2
Alpha Decay
Copy the following equation and write the correct answer
222
Rn
86
222
Rn
86
A
4
Y
He
+
Z
2
218
Po
+
84
4
He
2
Alpha Decay
Copy the following equation and write the correct answer
A
230
4
234
230
4
X
Z
U
92
Th
He
+
90
2
Th
He
+
90
2
Alpha Decay
Copy the following equation and write the correct answer
230
Th
90
230
Th
90
A
4
226
4
Y
He
+
Z
2
Ra
He
+
88
2
Alpha Decay
Copy the following equation and write the correct answer
A
214
4
218
214
4
X
Z
Po
84
Pb
He
+
82
2
Pb
He
+
82
2
Beta Decay
• A beta particle is a fast moving electron which
is emitted from the nucleus of an atom
undergoing radioactive decay.
• Beta decay occurs when a neutron changes
into a proton and an electron.
Beta Decay
• A result of beta decay, the nucleus has
one less neutron, but one extra proton.
• The atomic number increases by 1 and
the mass number stays the same.
0
-1
e
Beta Decay
218
218
Po
84
At
85
0
e
-1
Beta Decay
A
X
Z
218
Po
84
A
0
218
0
e
Y
+
Z+1
-1
At
+
85
e
-1
Beta Decay
234
A
234
234
Th
90
Th
90
Y
+
Z
Pa
+
91
0
e
-1
0
e
-1
Beta Decay
A
210
e
-1
210
210
0
X
Z
Tl
81
Pb
+
82
Pb
+
82
0
e
-1
Beta Decay
210
A
210
210
Bi
83
Bi
83
Y
+
Z
Po
+
84
0
e
-1
0
e
-1
Beta Decay
A
214
e
-1
214
214
0
X
Z
Pb
82
Bi
+
83
Bi
+
83
0
e
-1
Gamma Decay
Gamma rays are not charged particles like a and b
particles.
Gamma rays are electromagnetic radiation with high
frequency.
When atoms decay by emitting a or b particles to form a
new atom, the nuclei of the new atom formed may still
have too much energy to be completely stable.