Radioactive decay physical properties

All isotopes of plutonium are radioactive. The two isotopes that have found the most uses are Pu-238 and Pu-239. Pu-238 is produced by bombarding U-238 with deuterons in a cyclotron, creating neptunium-238 and two free neutrons. Np-238 has a half-life of about two days, and through beta decay it transmutates into plutonium-238. There are six allotropic metallic crystal forms of plutonium. They all have differing chemical and physical properties. The alpha (a) aUotrope is the only one that exists at normal room temperatures and pressures. The alpha allotrope of metallic plutonium is a silvery color that becomes yellowish as it oxidizes in air. AH the other allotropic forms exist at high temperatures. 

Calcium polyphosphate, dissociation and chain length, 4 48 Calcyclin, 46 454-456 Californium, 20 111 availability and price, 31 2 isotopes, 2 201 melting point, 31 6 oxidation state, 2 197 physical properties, 31 36 preparation and purification, 31 5, 7, 12, 33 apparatus, 31 34, 35 purity, 31 3 radioactivity, 31 33 vapor pressure, 31 6 Califomium-252, a-decay, 31 28 Californium oxide, metallothermic reduction, 31 7, 33... 

Most of the challenges associated with the handling of short-lived positron emitters are direct consequences of their physical properties, half-life and decay mode, from which also ensues very high maximum specific radioactivity and the associated practical minute amounts of material engaged in the radiosyntheses. 

Experimental investigations of spectroscopic and other physical-chemical properties of actinides are severely hampered by their radioactive decay and radiation which lead to chemical modifications of the systems under study. The diversity of properties of lanthanide and actinide compounds is unique due to the multitude of their valency forms (which can vary over a wide range) and because of the particular importance of relativistic effects. They are, therefore, of great interest, both for fundamental research and for the development of new technologies and materials. The most important practical problems involve storage and processing of radioactive waste and nuclear fuel, as well as pollution of the environment by radioactive waste, where most of the decayed elements are actinides. 

Potassium has three naturally occurring isotopes 39K (93.08%), 40K (0.01%), and 41K (6.91%). The radioactive decay of 4,)K to argon (40Ar), half-life of 109 years, makes it a useful tool for geological dating. Some physical properties of potassium are summarized in Table 1 (1—3). 

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). 

Table 3-2 lists important physical properties of radium and selected radium compounds. Radioactive properties of the four naturally-occurring radium isotopes are listed in Table 3-3. In addition to the naturally occurring isotopes, there are 12 other known isotopes of radium. The principal decay schemes of the uranium and thorium decay series that produce the naturally-occurring radium isotopes are presented in Figure 3-1.

The rate of radioactive decay of an element is the number of atoms emitting a radioactive ray per a unit time. The rate of decay is directly proportional to the initial amount of substance and the structure of the nuclei. On the other hand, the rate of decay is independent of the physical and chemical properties of a radioactive atom. Temperature does not affect the rate of decay. The rate of... 

Radiopharmaceuticals should have several specific characteristics that are a combination of the properties of the radionuclide used as the label and of the final radiopharmaceutical molecule itself. The radiopharmaceutical should ideally be easily produced (both the radionuclide and the unlabeled molecule) and readily available. The half-life of the radionuclide should be adequate to the diagnostic or therapeutic purpose for which it is designed. It has to be considered that radiopharmaceuticals disappear from the organism by a combination of two different processes. The biological half-life (showing the disappearance of a radiopharmaceutical from the body due to biological processes such as metabolization, excretion, etc.) and the physical half-life (due to the radioactive decay of the radionuclide). The combination of both parameters gives the effective half-life ... 

It is important to distinguish between radiation and radioactive contamination. Radiation is energy emitted by atoms that are unstable. Radiation travels through space to some extent—some kinds of radiation can only travel a few millimeters, whereas other types can travel for many meters. Radioactive contamination is the presence of radiation-emitting substances (radioactive materials or RAM) in a place where it is not desired. A patient may be contaminated with radioactive materials, but that patient will not be inherently radioactive and can be decontaminated. Radioactive materials, by comparison, are inherently radioactive—it is a physical property of that material in the same manner as mass or size—and they remain radioactive until they decay to stability. 

The physical properties of uranium and uranium compounds important in the nuclear fuel cycle and defense programs are listed in Table 3-2. The percent occurrence and radioactive properties of naturally occurring isotopes of uranium are listed in Table 3-3. The two decay series for the naturally occurring isotopes of uranium are shown in Table 3-4. 

The main physical properties of Rn are listed in Table ll-I, and its radioactive properties and place in the decay series are recorded in Table I l-II. Thoron (Tn), with a half-life of 54.5 sec., plays only a minor role in mineral exploration and actinon (An), with a half-life of 3.92 sec., can be considered insignificant in this regard. 

When a pure elemental gas, such as neon, was analyzed by a mass spectrometer, multiple peaks (two in the case of neon) were observed (see Fig. 1.11). Apparently, several kinds of atoms of the same element exist, differing only by their relative masses. Experiments on radioactive decay showed no differences in the chemical properties of these different forms of each element, so they all occupy the same place in the periodic table of the elements (see Chapter 3). Thus the different forms were named isotopes. Isotopes are identified by the chemical symbol for the element with a numerical superscript on the left side to specify the measured relative mass, for example °Ne and Ne. Although the existence of isotopes of the elements had been inferred from studies of the radioactive decay paths of uranium and other heavy elements, mass spectrometry provided confirmation of their existence and their physical characterization. Later, we discuss the properties of the elementary particles that account for the mass differences of isotopes. Here, we discuss mass spectrometry as a tool for measuring atomic and molecular masses and the development of the modern atomic mass scale. 

Radioactive decay is a property of the atomic nucleus and is evidence of nuclear instability. The rate of decay is unaffected by temperature, pressure, concentration, or any other chemical or physical condition but is characteristic of each individual radionuclide. 

Not much is known about astatine because it is very rare, is radioactive, and decays very quickly. Would you predict the chemical and physical properties of astatine to be more... 

U minerals and found the radioactive properties to be not a function of the physical or chemical forms of the uranium, but properties of the element itself. Using chemical separation methods, they isolated two new radioactive substances associated with the U minerals in 1898 and named them polonium and radium. In 1902 Ernest Rutherford and Frederick Soddy explained the nature of the process occurring in the natural decay chains as the radioactive decays of U and Th to produce new substances by transmutation. 

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