Radiochemistry is the chemistry of
radioactive materials, where radioactive isotopes of elements are used to study
the properties and chemical reactions of non-radioactive isotopes (often within
radiochemistry the absence of radioactivity leads to a substance being
described as being inactive as the isotopes are stable). Much of radiochemistry
deals with the use of radioactivity to study ordinary chemical reactions. This
is very different from radiation chemistry where the radiation levels are kept
too low to influence the chemistry.
All radioisotopes are unstable
isotopes of elements—undergo nuclear decay and emit some form of radiation. The
radiation emitted can be of several types including alpha, beta, gamma
radiation, proton and neutron emission along with neutrino and antiparticle
emission decay pathways.
α (alpha) radiation—the emission of
an alpha particle (which contains 2 protons and 2 neutrons) from an atomic
nucleus. When this occurs, the atom's atomic mass will decrease by 4 units and
atomic number will decrease by 2.
β (beta) radiation—the
transmutation of a neutron into an electron and a proton. After this happens,
the electron is emitted from the nucleus into the electron cloud.
γ (gamma) radiation—the emission of
electromagnetic energy (such as gamma rays) from the nucleus of an atom. This
usually occurs during alpha or beta radioactive decay.
These three types of radiation can
be distinguished by their difference in penetrating power.
Alpha can be stopped quite easily
by a few centimetres in air or a piece of paper and is equivalent to a helium
nucleus. Beta can be cut off by an aluminium sheet just a few millimetres thick
and are electrons. Gamma is the most penetrating of the three and is a massless
chargeless high energy photon. Gamma radiation requires an appreciable amount
of heavy metal radiation shielding (usually lead or barium-based) to reduce its
intensity.