Radioactivity and nuclear reactions

Some nuclei were formed that were stable, never undergoing further reactions. Others have lifetimes ranging from 10 years to 10 second. The usual method of describing nuclear decay is in terms of the half-life, or the time needed for half the nuclei to react. Because decay follows first-order kinetics, the half-life is a well-defined value, not dependent on the amount present. In addition to the overall curve of nuclear stability, which has its most stable region near atomic number Z = 26, combinations of protons and neutrons at each atomic number exhibit different stabilities. In some elements such as fluorine ( F), there is only one stable isotope (a specific combination of protons and neutrons). In others, such as chlorine, there are two 

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Quite often you hear only negative stories about nuclear reactions and radioactivity. Radioactivity can mutate DNA molecules and cause cancer. The use of nuclear reactors to produce energy can create nuclear waste, which can harm the environment. Nuclear power plants have been known to have accidents and expose many people to radioactive particles. Radioactive radon gas can be found in the homes that people live in. Nuclear warheads and nuclear weapons can cause mass destruction. On the other hand, there are many uses for radioisotopes that can be beneficial to our lives. In order for a radioisotope to be effective, it must be used properly and in the proper dosages. Some benefits of radioisotopes are described in the following chart. 

Skill 7.1a-Understand how mass-energy relationships in nuclear reactions and radioactive decay requires the relationship E=mc2... 

The energies of nuclear reactions and radioactive decays can only be considered with the aid of Einstein s equation relating mass and energy ... 

The most striking evidence for the existence of atoms comes from the observation of tracks formed by nuclear particles in cloud chambers, in solids and in photographic emulsions. The tracks reveal individual nuclear reactions and radioactive decay processes. From a detailed study of such tracks, the mass, charge and energy of the particle can be determined. 

Proceedings of the Symposium on the Chemical Effects Associated with Nuclear Reactions and Radioactive Transformations, I.A.E.A., Vienna, 1965. 

Radon-222 is an unstable nuclide that has been detected in the air of some homes. Its presence is a concern because of high health hazards associated with exposure to its radioactivity. Gaseous radon easily enters the lungs, and once it decays, the products are solids that remain embedded in lung tissue. Radon-222 transmutes to a stable nuclide by emitting a and P particles. The first four steps are a, a, P, p. Write this sequence of nuclear reactions and identify each product. 

Radioactive decay is a first-order process. See Chapter 20 for a discussion of half-lives related to nuclear reactions and other information on radioactivity. 

It is rare and found in "heavy" water (DOD), and it is present as only one part in almost 7,000 parts of regular water. Tritium ( T or H-3), another variety of heavy water (TOT), has nuclei consisting of one proton and two neutrons. It is man-made by nuclear reactions and is radioactive. 

ISOTOPES There are 50 Isotopes of Yttrium. Only one Is stable (Y-89), and It constitutes 100% of the element s natural existence on Earth. The other Isotopes range from Y-77 to Y-108 and are all produced artificially In nuclear reactions. The radioactive Isotopes have half-lives ranging from 105 nanoseconds to 106.65 days. 

The most important use of barium is as a scavenger in electronic tubes. The metal, often in powder form or as an alloy with aluminum, is employed to remove the last traces of gases from vacuum and television picture tubes. Alloys of barium have numerous applications. It is incorporated to lead alloy grids of acid batteries for better performance and added to molten steel and metals in deoxidizing alloys to lower the oxygen content. Thin films of barium are used as lubricant suitable at high temperatures on the rotors of anodes in vacuum X-ray tubes and on alloys used for spark plugs. A few radioactive isotopes of this element find applications in nuclear reactions and spectrometry. 

ALPHA DECAY. The emission of alpha particles by radioactive nuclei. The name alpha particle was applied in the earlier years of radioactivity investigations, before it was fully understood what alpha particles are. It is known now that alpha particles are the same as helium nuclei. When a radioactive nucleus emits an alpha particle, its atomic number decreases by Z = 2 and its mass number by A = 4. The process is a spontaneous nuclear reaction, and the radionuclide that undergoes the emission is known as an alpha emitter. 

Nuclear chemistry consists of a four-pronged endeavor made up of (a) studies of the chemical and physical properties of the heaviest elements where detection of radioactive decay is an essential part of the work, (b) studies of nuclear properties such as structure, reactions, and radioactive decay by people trained as chemists, (c) studies of macroscopic phenomena (such as geochronology or astrophysics) where nuclear processes are intimately involved, and (d) the application of measurement techniques based upon nuclear phenomena (such as nuclear medicine, activation analysis or radiotracers) to study scientific problems in a variety of fields. The principal activity or mainstream of nuclear chemistry involves those activities listed under part (b). 

Knowledge of fission and its consequences is important for the nuclear power industry and the related fields of nuclear waste management and environmental cleanup. From the point of view of basic research, fission is interesting in its own right as a large-scale collective motion of the nucleus, as an important exit channel for many nuclear reactions, and as a source of neutron-rich nuclei for nuclear structure studies and use as radioactive beams. 

One may rightfully raise the question as to why some products of nuclear reactions are radioactive while others are not. The answer concerns the stability of atomic nuclei. Essentially, any radioactive element, whether artificial or natural, can be considered abnormal. A nucleus that undergoes radioactive decay is in an unstable condition, and the process of decay always leads to stable isotopes. This tendency toward the achievement of stability is illustrated by the stepwise decay of naturally radioactive uranium to form a stable isotope of lead and the formation of stable carbon by the decay of artificial radioactive nitrogen. Although the conditions resulting in the instability of atomic nuclei are fairly well understood, further consideration of these factors is beyond the scope of this discussion. 

Kikuchi et al. (1994c) showed that the endohedral form of metallofullerenes was not affected by the recoil energy of the metal atom resulting from the emission of electrons in the S-decay in which nuclear reaction and decay processes are related to Ga Cg2, Tb C82, and Gd Cs2-Successful encapsulation of radioactive atoms inside the fullerene cage will widen the potential use of metallofullerenes not only in materials science and technology but in biological and even medical science. 

Research in nuclear and radiochemistry comprises Study of radioactive matter in nature, investigation of radioactive transmutations and of nuclear reactions by chemical methods, hot atom chemistry (chemical effects of nuclear reactions) and influence of chemical bonding on nuclear properties, production of radionuclides and labelled compounds, and the chemistry of radioelements - which represent more than a quarter of all chemical elements. 

Types of Radioactivity Nuclear Reactions and Energy Nuclear Tools... 

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