What is keeping the Earth so hot?
Nuclear Decay
Alpha, Beta, and Gamma
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.
Mass number = number of protons + number of neutrons
A
X
Z
Atomic number = number of protons
Element symbol
A
X
Z
A
= number of protons + number of neutrons
Z
= number of protons
A – Z = number of neutrons
Number of neutrons = Mass Number – Atomic Number
There are many types of uranium:
235
238
A
A
Z
Z
Number of protons
Number of protons
Number of neutrons
Number of neutrons
U
92
U
92
There are many types of uranium:
235
238
U
92
U
92
A
235
A
238
Z
92
Z
92
Number of protons
92
Number of protons
92
Number of neutrons
143
Number of neutrons
146
Isotopes of any particular element contain the same
number of protons, but different numbers of neutrons.
Most of the isotopes which occur naturally are stable.
A few naturally occurring isotopes and all of the manmade isotopes are unstable.
Unstable isotopes can become stable by releasing
different types of particles.
This process is called radioactive decay and the
elements which undergo this process are called
radioisotopes/radionuclides.
Radioactive Decay
Radioactive decay results in the emission of either:
• an alpha particle (a),
• a beta particle (b),
• or a gamma ray(g).
Alpha Decay
An alpha particle is identical to that of a helium nucleus.
It contains two protons and two neutrons.
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
222
Rn
86
A
4
Y
He
+
Z
2
Alpha Decay
222
Rn
86
222
Rn
86
A
4
Y
He
+
Z
2
218
Po
+
84
4
He
2
Alpha Decay
A
X
Z
230
4
Th
He
+
90
2
Alpha Decay
A
230
4
234
230
4
X
Z
U
92
Th
He
+
90
2
Th
He
+
90
2
Alpha Decay
230
Th
90
A
4
Y
He
+
Z
2
Alpha Decay
230
Th
90
230
Th
90
A
4
226
4
Y
He
+
Z
2
Ra
He
+
88
2
Alpha Decay
A
X
Z
214
4
Pb
He
+
82
2
Alpha Decay
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
As a result of beta decay, the nucleus has one less
neutron, but one extra proton.
The atomic number, Z, increases by 1 and the mass
number, A, stays the same.
Beta Decay
218
218
Po
84
At
85
b
-1
0
Beta Decay
A
X
Z
218
Po
84
A
b
-1
218
b
-1
Y
+
Z+1
Rn
+
85
0
0
Beta Decay
234
Th
90
A
Y
+
Z
b
-1
0
Beta Decay
234
A
b
-1
234
234
b
-1
Th
90
Th
90
Y
+
Z
P
91
+
0
0
Beta Decay
A
210
b
-1
210
210
b
-1
X
Z
Tl
81
Pb
+
82
Pb
+
82
0
0
Beta Decay
210
A
b
-1
210
210
b
-1
Bi
83
Bi
83
Y
+
Z
Po
+
84
0
0
Beta Decay
A
214
b
-1
214
214
b
-1
X
Z
Pb
82
Bi
+
83
Bi
+
83
0
0
Gamma Decay
G. Rays carry no charge and are very energetic.
They can be found at the high energy, high frequency
end of the E.M.S.
G. rays are pure energy (no mass)
The symbol for gamma decay is γ
They can penetrate up to 7 cm of lead
This means they are very
deadly
Gamma Decay
The End