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INAYA MEDICAL COLLEGE (IMC)
RAD 243- LECTURE 1
PHYSICAL BACKGROUND ATOMIC
STRUCTURE, NUCLEONS AND ACTIVITY
DR. MOHAMMED MOSTAFA EMAM
TOPIC
ISOTOPES
RADIOISOTOPES
RADIOACTVE DECAY
HALF LIFE
INTRODUCTION
• INTRODUCTION ABOUT RADIATION:
Radiation is energy in the form of waves or
streams of particles.
Based on the interaction with the matter
there are two types of radiation
1. Ionizing radiation
2. Non- ionizing radiation
TYPES OF RADIATION
ATOMS
• Where all matter begins?
Atoms are the basic building blocks of the
all the matters in this world.
All things both living and non living begins
with atoms only.
Atoms are elements like oxygen ,
hydrogen and carbon.
STRUCTURE OF AN ATOM
Proton
ISOTOPES
• An isotopes is a variant of a particular
chemical element.
• Isotopes of an element consists of a same
number of protons and different number of
neutrons.
• For example, hydrogen has 3 isotopes:
Hydrogen 1 : 1 proton and no neutrons
Hydrogen 2 : 1 proton and 1 neutron
Hydrogen 3 : 1 proton and 2 neutrons
The number of protons
present in atom is called
as Atomic Number.
The number of protons
and neutrons present in
atom is called as
Nuclear Number.
Isotope is stable when it
has a same number of
neutrons and protons.
RADIOISOTOPE
DEFINITION:
• Radioactive isotope or radioisotope, natural or
artificially created isotope of a chemical element
having an unstable nucleus that decays emitting
α, β and ϒ rays until stability reached.
• A radioisotope is an isotope of an element that
undergoes spontaneous decay and emits
radiation as it decays.
• During the decay process , it becomes less
radioactive overtime, eventually becoming stable.
• Once an atom reaches a stable configuration, it
no longer gives off radiation.
RADIOACTIVE DECAY
• Radioactive decay is the process in which an
unstable atomic nucleus loses energy by
emitting radiation in the form of particles or
electromagnetic waves.
• There are two forms of radioactive decay
Natural radioactivity
Artificial radioactivity
RADIOACTIVE DECAY
• Natural radioactivity:
This is the spontaneous disintegration of
naturally occurring radio–nuclides to form a
more stable nuclide with the emission of
radiations of alpha, beta and gamma.
• Artificial radioactivity:
This is the spontaneous disintegration of a
nuclide when bombarded with a fast moving
thermal neutron to produce a new nuclide
with the emission of radiations of alpha, beta
and gamma and a large amount heat.
RADIOACTIVE DECAY
• There are three types of radioactive emission:
α decay
β decay
ϒ decay
RADIOACTIVE DECAY
RADIOACTIVE DECAY
Proton mass ≈ Neutron mass
= 1 Atomic Mass Unit
RADIOACTIVE DECAY
α – decay:
• Alpha particles consists of large mass. Alpha
decay occurs when the atom ejects a particle
from the nucleus, which consists of two
neutrons and two protons.
• When alpha decay occurs, the atomic number
decreases up to 2 and the mass decreases by
4 and electrical charge of +2.
RADIOACTIVE DECAY
• Another example:
RADIOACTIVE DECAY
β – decay:
β particles are consists of small mass and -1
electrical charge. It is mainly emitted by
nucleus.
In basic β – decay, a neutron is turned into a
proton and an electron is emitted from the
nucleus.
The atomic number increases by 1 and mass
decreases slightly.
RADIOACTIVE DECAY
ϒ – emission:
Gamma radiation have high energy, short
wave length. It accompanies with alpha and
beta emission, but it’s usually not shown in a
balanced nuclear reaction.
Gamma is an electromagnetic wave or
photon which has no electrical charge and has
great penetrating power.
Gamma decay takes place when there is
residual energy in the nucleus following α or β
decay.
RADIOACTIVE DECAY
• The residual energy is released as a photon of
gamma radiation. Gamma decay generally
does not affect the mass or atomic number of
a radioisotope.
• Gamma radiation is similar to that of X- rays.
• E.g., Cobalt- 60(Co-60). Gamma rays are
focused on the tumor to destroy it.
HALF LIFE
• Radioactive half-life is the time it takes half
the radioactive atoms present to decay.
Before
After one half-life