TEACHER NOTES (2) – Nuclear Chemistry
12.A TOPIC 3 - TYPES OF RADIOACTIVE DECAY
1. Education Portal (tutorial) : Alpha, Beta, Gamma types of radiation
2. Reading Activity – Types of Radioactive Decay + Questions (sent to you earlier)
3. Notes (make your own )
Nuclear Reactions
Chemical reactions involve the breaking and forming of bonds between different atoms. In a nuclear reaction
the situation is different – in a nuclear reaction changes occur involving the number of protons, neutrons, or
electrons in a single atom.
Proton is symbolized 1
Electron
0
0
Neutron:
1
p
e
OR

n
1
-1
-1
0
Radioactive Decay – a spontaneous (natural – doesn’t require energy) process in which unstable nuclei lose
energy by emitting radiation (alpha, beta, gamma) to increase stability. Atoms of one element can change into
atoms of another element. Atoms with mass numbers around 60 are the most stable.
 Why do radioactive atoms (radioisotopes) emit radiation? Because their nuclei are unstable (has to do
with the neutron – proton ratio. Ex. C-12 is stable  neutron to proton ration is 1:1; C-14 is unstable 
neutron to proton ratio is 1.33 : 1.  too many neutrons causes a nucleus to be unstable).
 How do these atoms gain stability? By losing energy through radioactive decay.
Types of Radioactive Decay
A. Alpha Emission – an alpha particle () is 2 protons and 2 neutrons (or a helium nucleus) bound together and is
emitted from the unstable nucleus during radioactive decay.
α particle = Helium nucleus = High energy = heavy = low speed =(2+) charged particles= 42 He (helium-4) = 42α
 Example 1:
210
206
Po

Pb
84
4
He
2
+
82
polonium – 210
lead – 206
alpha particle
 Example 2:
238
92
U→
Uranium – 238
234
90
Th
+
Thorium – 234
4
2
He
alpha particle
 Clothes/skin/paper will shield you form alpha particles.
B. Beta Emission – a beta particle () is an electron emitted from the unstable nucleus when a neutron is converted to a
proton.
n → 11 p + 0−1e
β particle = electron = high energy = light = high speed =(1-) charged electrons =
1
0
0
-1e
= 0-1β
 Examples:
14
C
6
carbon – 14
14

N
+
7
nitrogen – 14
0
e
-1
beta particle
 Metal foil will shield you from beta particles.

C. Gamma Emission or gamma rays ( ) are high-energy electromagnetic waves emitted from a
nucleus as it changes from an excited state to a ground energy state. Very similar to light, but is
much more dangerous. Gamma emission usually occurs immediately following other types
of decay (alpha and beta) and account for most of the energy lost during the radioactive decay process.
γ “particle” (EM energy) = (short wavelength/high frequency) high energy photons = NO mass
charge = very penetrating (harmful) = 00γ
= NO
 Example:
238
92
U→
Uranium – 238
234
90
Th
+
Thorium – 234
4
2
He
+
2 00 (two gamma rays of two different frequencies)
alpha particle
gamma rays
 Lead or concrete will protect you from gamma rays.
Summary:
Property
Alpha(α)
Beta (β)
Composition
Alpha particles
Beta particles
What is it?
(Description of radiation)
Helium nuclei
4
4
2 He or 2α
Electrons
0
0
-1e or -1β
Charge
Speed
Energy
positive
2+
6.64 x 10-24 kg (heavy)
Decreases the mass
number by 4
Decreases the atomic
number by 2
Low (slow moving)
Low
negative
19.11 x 10-28 kg (light)
Converts a neutron into
proton and electron
Increases atomic number by
1
High (fast moving)
High
Relative penetrating power
Blocked by paper or clothing
Blocked by metal foil
Mass
How it changes the nucleus
Gamma ()
High-energy
electromagnetic radiation
Photons
0
0
neutral
0 (no charge)
0 (no mass)
No change in mass number
nor atomic number
Highest speed
Highest
(most penetrating)
Not completely blocked by
lead or concrete
12.B TOPIC 4 – Balancing Nuclear Equations
Need to remember:
In balanced nuclear equations, the sum of the mass numbers (superscripts) is balanced (equal) on both sides of the
equation.
In balanced nuclear equations, the sum of the atomic numbers (subscripts) is balanced (equal) on both sides of the
equation.
Example – Alpha Decay:
Answer:
228
88
Example – Beta Decay:
X + 0=60; x = 60
Answer:
60
27Co

x
y?
+
0
-1e
Ra
60
28
Ni
Y + (-1) = 27; y = 27+1 = 28
Characteristics of Chemical and Nuclear Reactions
Chemical reactions
Nuclear reactions
1. Occur when bonds are broken and formed
1. Occur when nuclei emit particles and/or rays
2. Atoms unchanged, rearranged
2. Atoms converted into atoms of another element
3. Involve only valence electrons
3. Involve p+, e-, n0
4. Release/absorb small amounts of energy
4. Release/absorb LARGE amount of energy
5. Reaction rate is NOT influenced by T’, P, concentration,
5. Reaction rate is influenced by T’, P, concentration,
catalysts
catalysts