Question: What Is Radioactivity? What is Radiation?
Unstable atomic nuclei will spontaneously decompose to form nuclei with a higher stability. The decomposition process is called radioactivity. The energy and particles which are released during the decomposition process are called radiation. When unstable nuclei decompose in nature, the process is referred to as natural radioactivity. When the unstable nuclei are prepared in the laboratory, the decomposition is called induced radioactivity.
Answer: There are three major types of natural radioactivity:
- Alpha Radiation
Alpha radiation consists of a stream of positively charged particles, called alpha particles, which have an atomic mass
of 4 and a charge of +2 (a helium nucleus). When an alpha particle is
ejected from a nucleus, the mass number of the nucleus decreases by four
units and the atomic number decreases by two units. For example:
23892U → 42He + 23490Th
The helium nucleus is the alpha particle.
- Beta RadiationBeta radiation is a stream of
electrons, called beta particles. When a beta particle is ejected, a
neutron in the nucleus is converted to a proton, so the mass number of
the nucleus is unchanged, but the atomic number increases by one unit.
23490 → 0-1e + 23491Pa
The electron is the beta particle.
- Gamma RadiationGamma rays are high-energy photons
with a very short wavelength (0.0005 to 0.1 nm). The emission of gamma
radiation results from an energy change within the atomic nucleus. Gamma
emission changes neither the atomic number nor the atomic mass. Alpha
and beta emission are often accompanied by gamma emission, as an excited
nucleus drops to a lower and more stable energy state.