Isotope with
unstable nucleus
Tendency to emit particles from the nucleus to
become stable (process known as nuclear decay)
They undergo Nuclear
Decay
Radioactive
Nucleus
New
Nucleus
+
The energy emitted from the
nucleus is called “Radiation”
Particles
Summary of Nuclear Chemistry – Common forms of radiation emitted from unstable nucleus
Name
Alpha
Beta
Positron
Symbol
α
β
β+
Representation
He
e
+e
Mass
Number
4
0
0
Charge
+2
-1
+1
When are they produced?
From heavy unstable nucleus after
nucleus particle rearrangements
occur. Formed by heavy mass
particles α (containing 2 protons
and 2 neutrons) which are emitted
from the nucleus
From unstable nucleus after
nucleus particle rearrangements
occur. Formed when a neutron is
transformed into:
proton + electron
Note: The high energy electron is
emitted from the nucleus
From unstable nucleus after
nucleus particle rearrangements
occur. Formed when a proton is
transformed into:
neutron + positron
Note: The positron is similar than
an electron, but with a positive (+)
charge. The positron is emitted
from the nucleus
Gamma
Rays
γ
γ
Chapter 9 Nuclear Chemistry
CHM1033 Prof. R. Duarte
0
0
From unstable nucleus after
nucleus particle rearrangements
occur. Formed when a positron and
an electron collide and their very
small masses are converted into
pure energy
Travel
distance
through air
Recommended
shield to prevent
exposure harm
Typical
sources
2 – 4 cm
(they collide
with air
molecules and
become He
atoms)
Lab coats, gloves,
paper clothing
(heavy damage by
ingestion)
Ra-226
U-238
Several
meters
through air
200 – 500 cm
Heavy clothes, lab
coats, gloves
Note: They can
pass through paper
into human skin
and penetrate 4-5
mm into body
tissue
C-14
Positron
particles
collide with
electrons
within the
electronic
cloud,
producing
gamma rays
Great
distance
through air
(~ 500 m)
Gamma radiation
can be extremely
hazardous. Very
dense shield is
required such as
lead or thick
concrete.
Note: They can
penetrate deeply
into human skin,
tissues and
organs. Example:
gamma emitting
devices (syringes)
are provided with
lead cover.
Gamma
rays are
usually
emitted in
conjunction
with other
types of
radiation
(Example in
conjunction
with alpha
radiation
from
uranium)