2. Learning Objectives
By the end of the section, you will be able to:
I. Understand the definition of Radioactivity
II. Remember the SI unit of radioactivity
III. Classification of Radioactivity
IV. Know the important of Radioactivity
V. Discovery of Radioactivity
VI. Understand how is radioactivity harmful to
humans?
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3. 3
Radioactivity {Definitions}
1. A Radioactivity is the transformation of
an atom with emission of rays.
2. Radioactivity is the emission of elementary
particles by some atoms when their
unstable nuclei disintegrate(see half-life).
3. Radioactivity is the process by which an
unstable atomic nucleus loses energy by
emitting radiation
4. Radioactivity {Definitions}
Radioactivity :is the spontaneous emissions of
particles and energy from an unstable nucleus of an
atom
Nucleons :are protons and neutrons in the nucleus
of an atom.
Nuclide: : is how we refer to many isotope of an
atom
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5. SI unit of radioactivity
The SI unit of radioactivity is the Becquerel(Bq).
Other units of radioactivity include the curie , gray,
And Sievert.
One Becquerel is defined to be one decay or
disintegration per second.
The unit is named in honor of the discoverer of
radioactivity French scientists Henri Becquerel.
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6. Classification of Radioactivity
Types of Radioactivity
Alpha, beta and gamma decay are three
common processes through which
radioactivity materials lose energy.
The first three types of radioactivity decay to
be discovered were alpha, beta and gamma
decay .
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8. 8
Alpha decay & Beta decay
Alpha decay :An alpha decay (A=4, Z=2)
is emitted from the nucleus resulting in a
daughter nucleus (A-4, Z-2)
Beta decay : A beta practical is emitted from
the nucleus of an atom, raising the atomic
number of the atom by one if particle is
negatively charged, lowering it by one if
positively charged
12. Discovery of Radioactivity
In 1897, Becquerel accidently
discovered radioactivity in pitchblende
(a uranium mineral ) while studying
sunlight induced fluorescence of
various minerals .This mineral was
found to produce a photographic
image, even through black paper .
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13. How Radioactivity is harmful
Exposure to large amounts of
radioactivity can cause nausea,
vomiting, hair loss, destruction of
intestinal lining, central nervous system
damage, and death. It also causes
DNA damage and raises the risk of
cancer, particularly in young children
and fetuses.
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