Nuclear Chemistry
“Bravo” Test 1954 – 15,000 kilotons
Radioactivity and Nuclear Energy
Objective: To learn the types of
radioactive decay
Objective: To learn to write nuclear
equations that describes radioactive
decay
Objective: To learn how one element may
be changed into another by particle
bombardment
What makes an atom radioactive?
Radioactivity: the spontaneous
decomposition of a nucleus to form
another nucleus and produce one or more
particles.
-the neutrons act as glue holding the
nucleus together
-the heavier the atom, the more likely it
is to be radioactive
-if the number of protons in the nucleus
exceeds 83, then the nuclide is
radioactive
Types of Radioactive Decay
alpha production (a, He): helium nucleus
U  He 
238
92
4
2
234
90
Th
beta production (b, e):
Th 
234
90
234
91
Pa  e
0
1
 gamma ray production (g):
U  He 
238
92
4
2
Th  2 g
234
90
0
0
Specifying Isotopes
A
X
Z
X = the symbol of the
element
A = mass number
(protons + neutrons)
Z = the atomic number
(number of protons)
5
Nuclear Symbols
Mass number, A
(p+ + no)
235
92
U
Atomic number, Z
(number of p+)
Element symbol
Key to Understanding
Nuclear Reactions
In nuclear reactions, both the atomic
number Z and the mass number A must be
conserved
Balancing Nuclear Equations
222
226 = 4 + ____
226
88
Ra  a 
4
2
222
86
Rn
88 = 2 + ___
86
Atomic number 86 is radon, Rn
Alpha Decay
Alpha production (a):
an alpha particle is a
helium nucleus
4
2
He or a
2
U  He 
238
92
4
2
U a
238
92
4
2
4
2
2
234
90
Th
234
90
Th
Alpha decay is limited to heavy, radioactive
nuclei
Alpha (α) Decay
P+N
P
E1
P+N -4
P-2
E2 +
4
He
2
an alpha particle (helium nucleus) is produced
Alpha
Radiation
Limited to
VERY large
nucleii.
Example of Alpha Decay
222
88
Ra
218
86
4
Rn + 2 He
Radium 222 decays by α particle production to Radon 218
Beta Decay
Beta production (b):
A beta particle is an
electron ejected from
the nucleus
0
1
Th 
234
91
Th 
234
91
234
90
234
90
e or
0
1
b
Pa  e
0
1
Pa  b
0
1
Beta emission converts a neutron to a proton
Beta (β) Decay
P+N
P
E1
P+N
P+1
E2 +
e
-1
0
Beta emission converts a neutron to a proton
Beta
Radiation
Converts a
neutron into
a proton.
Example of Beta Decay
Notice the mass of the beta
particle is zero; it is so small
that is must be neglected.
14
6
C
14
7
N + -1e
0
Example of Beta Decay
234
90
Th
234
91
Pa + -1e
0
Thorium 234 decays by β particle production to Protactinium 234
(notice: no change in mass number A, and an increase of 1 in atomic
number Z)
Gamma Ray Production
Gamma ray production (g):
U  He
238
92
4
2
Th  2 g
234
90
0
0
Gamma rays are high energy photons
produced in association with other forms of
decay.
Gamma rays are massless and do not, by
themselves, change the nucleus
Gamma Ray Production
Gamma ray production (g):
U  He 
238
92
4
2
Gamma rays are high
energy photons produced in
association with other
forms of decay.
Gamma rays are
massless and do not,
by themselves,
change the nucleus
Th  2 g
234
90
0
0
Positron Production
Positron emission:
Positrons are the antiparticle of the electron
22
11
0
1
e
Na  e  Ne
0
1
22
10
Positron emission converts a proton to a neutron
Positron Production
P+N
P
E1
P+N
P-1
E2 +
e
1
0
Positron emission converts a proton to a neutron
Electron Capture
Electron capture: (inner-orbital electron
is captured by the nucleus)
Hg  e 
201
80
0
1
Au  g
201
79
0
0
Electron capture converts a proton to a
neutron
Alpha Particle
Emission
4
Symbol 2
Mass
He
2
a
4
or 2
2
Heavy
How it changes 
the nucleus

Decreases the 
mass number
by 4
Decreases the 
atomic number
by 2
Beta Particle
Emission
0
1
e
0
or 1
b
Light
Converts a
neutron into a
proton
Increases
atomic number
by 1
Gamma Ray
Emission
0
0
g
No Mass
No change to the
nucleus
Penetration
Low
Medium
High
Protection
provided by…
Skin
Paper, clothing
Lead
Danger
Low
Medium
High
Types of Radiation
Nuclear
Stability
Decay will occur in
such a way as to
return a nucleus to
the band (line) of
stability.
The most stable
nuclide is Iron-56
If Z > 83, the
nuclide is radioactive
A Decay
Series
A radioactive nucleus
reaches a stable state
by a series of steps
Graphic – Wikimedia Commons User Tosaka
Alpha Particle
Emission
4
Symbol 2
Mass
He
2
a
4
or 2
2
Heavy
How it changes 
the nucleus

Decreases the 
mass number
by 4
Decreases the 
atomic number
by 2
Beta Particle
Emission
0
1
e
0
or 1
b
Light
Converts a
neutron into a
proton
Increases
atomic number
by 1
Gamma Ray
Emission
0
0
g
No Mass
No change to the
nucleus
Penetration
Low
Medium
High
Protection
provided by…
Skin
Paper, clothing
Lead
Danger
Low
Medium
High