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Alpha decay
Alpha decay
or
a-decay
is a type of
radioactive decay
in which an
atomic nucleus
emits an
alpha particle
(helium nucleus) and thereby transforms or 'decays' into an atom with a
mass number
that is reduced by four and an
atomic number
that is reduced by two. An
alpha particle
is identical to the nucleus of a
helium-4
atom, which consists of two
protons
and two
neutrons
. For example,
uranium-238
decays to form
thorium-234
:
or
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