Thermodynamic stability is the potential energy of a particular nucleus as compared to the sum of the potential energies of its component protons and neutrons. Many nuclei go through radioactive decay, in this process the nuclei decomposes, forms another nucleus, and produces one or more particles. There are different decay processes such as, alpha-particle production, spontaneous fission, beta-particle production, gamma ray production, and positron production. Decay occurs until a stable nuclei is formed.

The Kinetics of Radioactive Decay

Radioactive decay follows first-order kinetics. The half-life of a radioactive sample is the time required for the amount of the nuclide to reach half the original amount. The half-life for a first-order process is constant.

Nuclear Transformations

A nuclear transformation is the change of one element into another. Many nuclear transformations have been achieved by using particle accelerators. A particle accelerator is a device used to accelerate nuclear particles to very high speeds. Due to the electrostatic repulsion between the target nucleus and a positive ion, accelerators are needed when positive ions are used as bombarding particles. The particle which is accelerated to a high velocity, can overcome the repulsion and penetrate the target nucleus, which affects the transformation. Neutrons are also employed as bombarding particles to effect nuclear transformations. Neutrons are readily absorbed by target nucleus?because they have no charge and therefore are not repelled electrostatically by the target nucleus.

Detection and Uses of Radioactivity

The Geiger counter is an instrument that measures the rate of radioactive decay based on the ions and electrons produced as a radioactive particle passes through a gas filled chamber. Another instrument used to measure radioactivity is the scintillation counter. The scintillation counter is an instrument that measures radioactive decay by sensing the flashes of light produced in a substance by the radiation.

Radioactivity is very useful. Radiocarbon dating (carbon-14 dating) is used for dating ancient articles made from wood or cloth. A radiotracer is a radioactive nuclide, introduced into an organism for diagnostic purposes, whose pathway can be traced by monitoring its radioactivity. Radiotracers are used for learning about biological systems, for detection of diseases, for monitoring the action and effectiveness of drugs, and for early detection of pregnancy.

Thermodynamic stability of the Nucleus

The thermodynamic stability of a nucleus can be obtained by calculating the change in potential energy that would occur if that nucleus were formed from its constituent protons and neutrons. The thermodynamic stability of a particular nucleus is normally represented as energy released per nucleon. The energy needed to decompose a nucleus into its component nucleons is called the binding energy.

Nuclear Fission and Fusion

Fission is the process of using a neutron to split a heavy nuclei into two smaller nuclei. Fission bombs were used on the cities of Hiroshima and Nagasaki. A fission bomb operates by suddenly combining subcritical masses of fissionable material to form a supercritical mass, which produces an explosion.

Fusion is the process of combining two light nuclei to form a heavier, more stable nucleus. Stars produce their energy through nuclear fusion. For two protons to bind together and release energy, they must get very close together. However, protons repel each other electrostatically. In order to get the protons close they need to be ¡°shot¡± at each other at high velocities to overcome the electrostatic repulsion.

Effects of Radiation

Radioactive elements are sources of high-energy particles. However radioactive elements are potentially hazardous, however the results are quite subtle. Somatic damage is damage to organisms, which results in sickness or death. Effects of radiation can be seen right away if a massive dose of radiation is received. If a small dose of radiation is received, the damage may appear years later, which is usually in the form of cancer. Genetic damage is damage to the genetic machinery, which produces malfunctions in the offspring of the organism.

The higher the energy content of the radiation, the more damage it can cause. Radiation doses are measured in rads. One rad corresponds to 10^-2J of energy deposited per kilogram of the organism. The particles and rays produced in radioactive processes vary in penetration of the human tissue. Gamma rays are highly penetrating, beta particles can penetrate about 1cm, and alpha particles are stopped by the skin.