Radioactive elements are those that emit radiation. There are three different types of radiation alpha, beta, and gamma radiation. They all have different specific properties.
Radioactivity is a property that exhibited by certain types of matter of emitting energy and subatomic particles spontaneously. It is attributing to individual atomic nuclei. An unstable nucleus will decay spontaneously, into a more stable nucleus.
This all phenomena occur only a few specific ways by emitting certain particles or specific forms of electromagnetic energy. Radioactive decay is a property of few naturally occurring elements as well as of artificially produced isotopes of the different elements.
The decay of radioactive elements is expressed in terms of its half-life. This is the time that required for one-half of any given quantity of the isotope to decay. Half-lives of the radioactive element are from more than 1,000,000,000 years for some nuclei to less than 10−9 seconds.
The product of a radioactive decay process is called the daughter of the parent isotope that may itself be unstable, in which case it both will decay. The process continues until a stable nucleus has been formed.
The Nature of Radioactive Emissions
The emissions of spontaneous radioactive decay are alpha (α) particle, beta (β) particle and gamma (γ) ray. The alpha particle is actually consisting of four helium nucleus, with two positive charges and two neutral neutrons (4/2He).
The neutral helium atom has 2 electrons outside the nucleus and its nucleus balancing these two charges. Beta particles may be negatively beta charged particles (beta minus, symbol e−), or positively beta charged particles (beta plus, symbol e+).
The beta minus particle is actually an electron that created in the nucleus during beta decay without any relationship to the orbital electron cloud of the atom. The beta plus particles are also called positron.
This is the antiparticle of the electron; when brought together; two such particles will mutually annihilate each other. Gamma rays are electromagnetic radiations such as microwaves, light waves, radio waves and X-rays.
Gamma radioactivity also produces the neutrino and antineutrino particles that have no charge and very less mass. In the less common forms of radioactivity, fission fragments, protons or neutrons may be also emitted.
Fission fragments particles are themselves complex nuclei with usually between 1/3 and 2/3 the charge number Z and mass number A of the parent nucleus. Protons and neutrons and are basic building blocks of complex nuclei, having an approximately unit mass on the atomic scale and having zero charges or unit positive charge.
The neutron can’t longer exist in the Free State. It is captured by nuclei in the matter. Otherwise in free space neutron will undergo beta-minus decay to a proton, electron, and an antineutrino with a half-life that is 12.8 minutes.
There are three types of radiations:
These are positively charged particle. The charge to mass ratio is about one half that of a singly charged hydrogen atom. It became clear afterward that these rays were energetic nuclei of helium. An alpha particle or a helium nucleus is composed of two protons and two neutrons, totally four nucleons.
It has strong capability of ionization. When alpha particles are passing through the material with high density of ions is created in a cylindrical shape along the path. It is called the cylindrical ionization.
High energy alpha particles lose their energy very fast and can only travel through a short distance. Alpha particles with energy 5.3 MeV is able to penetrate through the distance of 3.8 cm thickness of air. A piece of paper having a common thickness is able to stop those alpha particles. Alpha particles cannot penetrate through human skin.
Beta rays are negatively charged particles. Beta rays interact with atoms. They lose energy by exciting or ionizing atoms to higher energy states or free states while traveling in the materials. Ion density created by electrons is far less than those from alpha particles with the same energy.
The penetration power of the beta rays is much stronger than the alpha rays. Electrons with the energy of 5.3 MeV is able to penetrate through a distance of 20 m thickness of air. Penetration power is approximately 500 times of alpha particles.
Electrons with the energy of 5.3 MeV is able to penetrate through the width of 10 mm in aluminum and 2 mm in lead. Beta rays are much more dangerous than alpha rays.
These are electrically neutral charged particles with properties that are identical with energetic photons. Photoelectric effects of gamma rays are less than 0.4 MeV (Eγ < 0.4 MeV). Compton effect of gamma rays are lies between 0.4MeV to 5MeV (0.4 MeV < Eγ < 5 MeV).
Pair production effects of gamma rays are greater than 5MeV (Eγ > 5 MeV)