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RADIOACTIVITY
Radioactivity is the process in which an
unstable atomic nucleus emits charged
particles and energy.
 Any atom containing an unstable nucleus is
called a radioactive isotope, or radioisotope for
short.
 Uranium-238 is an example of a radioisotope.

RADIOISOTOPES
Unlike stable isotopes, radioisotopes
spontaneously change into other isotopes over
time.
 When this happens, it is called nuclear decay
 During nuclear decay, atoms of one element
can change into atoms of a different element
altogether.

TYPES OF NUCLEAR RADIATION
Nuclear radiation is charged particles and
energy that are emitted from the nuclei of
radioisotopes.
 Common types of nuclear radiation include
alpha particles, beta particles, and gamma
rays.

ALPHA DECAY
Some samples of radioisotopes emit alpha
particles.
 Example: Uranium-238
 An alpha particle is a positively charged particle
made up of two protons and two neutrons.

4
Symbols for alpha
particles
2
He
BETA DECAY
Some samples of radioisotopes release
negatively charged radiation called beta
particles
 A beta particle is an electron emitted by an
unstable nucleus.

0
Symbols for beta
particles
-1
e
GAMMA DECAY
Not all nuclear radiation consists of charged
particles.
 A gamma ray is a penetrating ray of energy
emitted by an unstable nucleus.
 Gamma radiation has no mass and no charge.

Symbol for gamma radiation
EFFECTS OF NUCLEAR RADIATION
You are exposed to nuclear radiation every day,
most of this being background radiation, which
occurs naturally in the environment.
 The radioisotopes in air, rocks, water, plants
and animals contribute to background
radiation.
 BR levels are generally low enough to be safe.

The mineral autunite is an
Important source of uranium.
Cosmic rays are streams of electrically charged particles. Collisions between
cosmic rays And Earth’s atmosphere shower the surface below
with nuclear radiation.
EFFECTS CONT’D
When nuclear radiation exceeds background
levels, it can damage the cells and tissues of
your body.
 Nuclear radiation can ionize atoms making your
cells no longer function properly.

DETECTING NUCLEAR RADIATION
Scientific instruments can detect nuclear
radiation since you cant see, hear, or feel the
radioactivity around you.
 Devices that are used to detect nuclear
radiation include Geiger counters and film
badges.

GEIGER COUNTERS

The greater the amount of nuclear radiation,
the greater the electric current produced in the
gas filled tube attached to the Geiger counter.
FILM BADGES
People who work with radioactive materials
wear film badges to monitor their exposure to
nuclear radiation.
 The exposure on the film indicates the amount
of radiation exposure for the person wearing
the badge.

HALF-LIFE
Every radioisotope decays at a specific rate
that can be expressed as a half-life.
 A half-life is the time required for one-half of a
sample of a radioisotope to decay.
 After one half-life, half the atoms in a
radioactive sample have decayed, while the
other half remain unchanged.
 After two half-lives, half of the remaining half
decays, etc.
