• Historical outline of radioactivity: work of
Becquerel (discovery of radiation from
uranium salts); Marie and Pierre Curie
(discovery of polonium and radium).
• Widespread occurrence of radioactivity.
Antoine Henri Becquerel
• In 1896, while investigating
uranium salts, Becquerel
radioactivity . Becquerel
found that the photographic
plates were fully exposed
when in contact with
• developed a theory of
for isolating radioactive
isotopes, and discovered
two new elements,
Polonium and Radium
Natural Radiation comes from
Sources in the earth that contain
Sources from space in the form of
Sources in the atmosphere,
particularly from Radon gas that is
released from the Earth's crust.
About 15% of background radiation
comes from medical X-rays and
About 3% of background radiation
comes from other man-made sources
such as: nuclear testing, power plants,
and smoke detectors.
• Pierre discovered nuclear
energy, by identifying the
continuous emission of heat
from Radium particles. He
also investigated the radiation
emissions of radioactive
substances, which lead to the
discovery of Alpha, Beta and
• Alpha, beta and gamma radiation (nature and
penetrating ability).One example each of:
• an α-emitter, e.g. 241Am
• a β-emitter, e.g. 14C
• a γ-emitter, e.g. 60Co.
• Is the spontaneous
breaking up of
unstable nuclei with
the emission of one or
more types of
• There are three types
alpha, beta and gamma
• A Radioisotope (radionuclide) is an atom
with an unstable nucleus.
• Change of one element into another
• Rutherford confirmed the artificial
transmutation of nitrogen. Alpha particles
were allowed to pass through nitrogen gas;
when one struck a nitrogen nucleus, a
hydrogen nucleus was ejected, and an
oxygen nucleus formed.
• Time taken for
half of the nuclei
in any given
sample to decay
• Medical—.gamma rays kill cancerous cells
and sterilises equipment
• Archaeological—after a living thing dies
the amount of C-14 decreases. Used to
determine the age of a plant/animal
• Food—gamma rays kill disease causing
A particular slide catching your eye?
Clipping is a handy way to collect important slides you want to go back to later.