SECTION SUMMARY
25.1 Nuclear Radiation Summary:
Isotopes with unstable nuclei are radioactive and are called radioisotopes. The nuclei of
radioisotopes decay to stable nuclei plus emission of large amounts of energy. The radiation may
be alpha, beta, or gamma. Alpha radiation consists of alpha particles (positively charged helium
nuclei) that are easily stopped by a sheet of paper. Beta radiation is composed of fast-moving
particles, which are electrons. Beta radiation is more penetrating than alpha radiation. It is
stopped by metal foil. Gamma radiation is electromagnetic radiation. Gamma radiation has no
mass or electrical charge. It is extremely penetrating. Concrete bricks and lead reduce the
intensity of gamma radiation but do not completely stop it.
When a radioisotope decays, beta radiation sometimes is emitted.
U + 10 e  239
This equation is never true because in beta radiation, the
92 U
neutron breaks apart into a proton, which remains in the nucleus, and a fast moving electron
which is released. The following beta radiation is correct:
238
92
238
92
U

0
1
e +
238
93
Np
Also, in beta radiation when the neutron breaks apart into a proton, causing the atomic
number increase by 1 and the mass number stay the same.
25.1 Nuclear Radiation Vocabulary Terms:
radioactivity:
the process by which nuclei emit particles and rays
radiation:
the penetrating rays and particles emitted by a radioactive
source
radioisotopes:
an isotope that has an unstable nucleus and undergoes
radioactive decay
alpha particle:
a positively charged particle emitted from certain radioactive
nuclei; it consists of two protons and two neutrons and is
identical to the nucleus of a helium atom
beta particle:
an electron resulting from the breaking apart of neutrons in an
atom
gamma ray:
a high-energy photon emitted by a radioisotope
The End of the Summary