Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability. Because the nucleus experiences the intense conflictbetween the two strongest forces in nature, it should not be surprising that there are many nuclearisotopes which are unstable and emit some kind of radiation. The most common types of radiation are called alpha, beta, and gamma radiation, but there are several other varieties of radioactive decay.Radioactive decay rates are normally stated in terms of theirhalf-lives, and the half-life of a given nuclear species isrelated to its radiation risk. The different types of radioactivitylead to different decay paths which transmute the nuclei intoother chemical elements. Examining the amounts of the decayproducts makes possibleradioactive dating.Radiation from nuclear sources is distributed equally in alldirections, obeying theinverse square law.
Radioactivity is the process whereby unstable atomic nuclei releaseenergetic subatomic particles. The word radioactivity is also used to refer to the subatomic particles themselves. This phenomenon is observed in the heavy elements, like uranium, and unstable isotopes, like carbon-14. Radioactivity was first discovered in 1896 by the French scientist Henri Becquerel, after which the SI unit for radiation, the Becquerel, is named. Becquerel discovered that uranium salts were able to blacken a photographic plate placed in the dark, even through a paper barrier. Subsequent experiments distinguished three distinct types of radiation -- alpha particles, beta particles, and gamma rays. These are positively charged, negatively charged, and neutral, respectively. In the United States, human exposure to radioactivity is measured in rads, where one rad represents 0.01 joule of energy absorbed per kilogram of tissue.Radioactivity is a random process, meaning that it is physically impossible to predict whether or not a given atomic nucleus will decay and emit radiation at any given moment. Rather, radioactivity is quantified using half-life, which is the period of time it takes for half of the given nuclei to decay. Half-life applies to a sample of any size, from a microscopicquantity to all the atoms of that type in the universe. Half-life varies widely, from a couple seconds (Astatine-218) to billions of years (Uranium-238).
French physics Professor Antoine Henri Becquerel discovered that uranium compounds produced rays that blacked photographic plates. Elements that spontaneously emit energetic particles and rays from theiratomic nuclei have radioactive property or undergo radioactivity. These emitted particles or rays are called radiation. An elemental material (such as uranium) that emits radiation is called radioactive material. Most, but not all, atomic nuclei are stable i.e. not radioactive. Radioactivity is a naturally occurring process that occurs when an unstable nucleus goes through a transformation, moving to a lowerenergy state accessible to the nucleus. The nucleus splits apart releasing energy in order to become stable. Radiation emitted from a nucleus can be particles, such as alpha particles (2 protons, 2 neutrons), beta particles (electrons) as well as neutrons, and the electromagnetic gamma rays and x-rays. A radioactive material can be in solid, liquid or gaseous form. They arefound naturally in our environment and commonly used in society. Naturalsources of radiation in the environment, such as the continuous shower of cosmic rays from space and radioactive material in the ground and air (some of which is a result of atmospheric atomic bomb testing, and Chernobyl), create a "background" radiation exposure that we are all subject to.
Alpha Radioactivity Composed of two protons and two neutrons, the alpha particle is a nucleus of the element helium. Because of its very large mass (more than 7000 times the mass of the beta particle) and its charge, it has a very short range. It is not suitable for radiation therapy since its range is less than a tenth of a millimeter inside the body. Its main radiation hazard comes when it is ingested into the body; it has great destructive power within its short range. In contact with fast-growing membranes and living cells, it is positioned for maximum damage. Alpha particle emission is modeled as a barrier penetration process. The alpha particle is the nucleus of the helium atom and is the nucleus of highest stability
Henri Becquerels experiment is shown in the picture below:
Radioactivity Decay Professionals often specialize in a certain areaof study, such as radioactivity, decay, fusion, or atomic interactions.Using established scientific methods, nuclear chemists and physicists design highly-detailed, controlled experiments. Radioactivity is a random process, meaning that it is physically impossible to predict whether or not a given atomic nucleus will decay and emit radiation at any given moment.Rather, radioactivity is quantified using half-life, which is the period of time it takes for half of the given nuclei to decay. Iodine Radioactivity At the start of the testing procedure, patients swallow the radioactive iodine and wait for a period of six to 24 hours before returning to have the thyroids radioactivity assessed. During the radioactive iodine uptake test, which only takes a few minutes, the patient sits upright in a chair while a probe is positioned several inches in front of the thyroid gland. Patients normally refrain from eating and drinking for a couple of hours after treatment, and are then encouraged to take plenty of fluids to flushradioactivity from the body. As one of the effects of radioactive iodine ablation is to make patients a little radioactive, patients are required to stay in a room by themselves after treatment.
Tritium RadioactivityIn small doses, radioactivity is a usefulprocess that can be harnessed by man. For example, nuclear reactors exploit radioactivity to generate heat. Phosphorescent materials sometimes include small quantities of radioactive atoms. Radioactivity Effects : Materials containing carbon-14 can be In small doses, radioactivity is a useful placed in geological time using a process that can be harnessed by man.process known as radiocarbon dating, in For example, nuclear reactors which the amount of carbon-14 in the exploit radioactivity to generate heat. material is used to determine its age. Phosphorescent materials sometimesTerrestrial radiation is the second major include small quantities of radioactive source of natural radioactivity. This atoms.radiation comes from isotopes of carbon A request to borrow a car may, in fact, and potassium, as well as thorium and go no further than the objective uranium, which may be found in soil, explicitly stated. The claimed cause rocks, or water. and effect relationship simply does not exist.
WHAT IS RADIOISOTOPES?Radioisotopes are isotopes that areunstable and release radiation. A radioisotopes is an atom with an unstable nucleus, characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or via internal conversion. During this process, the radionuclide is said to undergo radioactive decay, resulting in the emission of gamma ray and subatomic particles such as alpha or beta particles. These emissions constitute ionizing radiation. Radioisotopes occur naturally, or can be produced artificially. Radioisotopes are often referred to by chemists and physicists as radioactive isotopes or radionuclide. Radioisotopes with suitable half-lives play an important part in a number of technologies (for example, nuclear medicine). Radioisotopes can also present both real and perceived dangers to health..
Radioisotopes produced with nuclear reactors exploit the high flux of neutrons present. These neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is thallium-201 and iridium-192. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high neutron cross-section. They are radioactive isotopes An element has a characteristic number of protons (P) in its nucleus. Atoms of the element may have various numbers of neutrons (N) in the nucleus, typically close to P. For each element, we can gather naturally occurring samples and measure the number of neutrons N found in the nuclei, and find the average. The mass of each atom in the sample is roughly P+N. In the sample, one value of N will be predominant, with other numbers (other atomic masses) being less common, and typically heavier. They are less common because they are less stable, and are likely to break down (emitting radioactive particles) into other isotopes. If two atoms of an element have different atomic masses (different Ns), then we call them isotopes of the element. The most stable isotope of an element (the longest-lived isotope) will be the one mostly commonly occurring in nature, as other isotopes will tend to break down and become rarer. A radioisotope is an unstable isotope of an atom with a short enough half-life to cause measurable amounts of radioactive particles to be emitted.
Uses Of RadioactivitySterilization of medical instruments and food is another common application of radiation. By subjecting the instruments and food to concentrated beams of radiation, we can kill microorganisms that cause contamination and disease. Because this is done with high energy radiation sources using electromagnetic energy, there is no fear of residual radiation. Also, the instruments and food may be handled without fear of radiation poisoning. Radiation sources are extremely important to the manufacturing industries throughout the world. They are commonly employed by nondestructive testing personnel to monitor materials and processes in the making of the products we see and use every day. Trained technicians use radiography to image materials and products much like a dentist uses radiation to x-ray your teeth for cavities. There are many industrial applications that rely on radioactivity to assist in determining if the material or product is internally sound and fit for its application.
Uses of Radioisotopes Radioisotopes are also a method of treatment in hemopoietic forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources sterilise syringes and other medical equipment. In biochemistry and genetics, radionuclides label molecules and allow tracing chemical and physiological processes occurring in living organisms, such as DNA replication or amino acid transport. In food preservation, radiation is used to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables. In industry, and in mining, radionuclides examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.