If a nucleus has too many neutrons
the most likely form of decay will be the
emission of an electron from the nucleus.
These high-energy electrons are known as beta particles
(
).
Independent electrons do not exist
in the nucleus. The beta particle is formed by the instant transformation of
a neutron into a proton
plus an energetic electron which then
escapes from the nucleus.
An example of beta decay is the decay of tritium (
H) into
He
(Fig2.2.
):
H