Radiation nuclear

Under certain conditions, some nuclei can emit alpha, beta, or gamma radiation. 

Real-World Reading Link If you wake up while it is still dark, the glowing numbers on your clock let you know what time it is. Many clocks use a type of radiation to make the numbers glow. The word radiation might cause you to think about nuclear power plants or dangerous, highly radioactive substances. However, less dangerous forms of radiation are often used in everyday objects, such as clocks. 

Involve only valence electrons Associated with small energy changes 

Atoms keep the same identity although they might gain, lose, or share electrons, and form new substances Temperature, pressure, concentration, and catalysts affect reaction rates 

The work of Marie and Pierre Curie was extremely important in establishing the origin of radioactivity and developing the field of nuclear chemistry. In 1898, the Curies identified two new elements, polonium and radium, on the basis of their radioactivity. Henri Becquerel and the Curies shared the 1903 Nobel Prize in Physics for their work. Marie Curie also received the 1911 Nobel Prize in Chemistry for her work with polonium and radium. 

You may recall from Chapter 4 that the nuclei of some atoms are unstable and undergo nuclear reactions. In this chapter you will study nuclear chemistry, which is concerned with the structure of atomic nuclei and the changes they undergo. An applicahon of a nuclear reaction is shown in the photo of the human neck and skull. Table 25-1 offers a comparison of chemical and nuclear reactions. 

Occur when bonds are broken and formed. 1. Occur when nuciei emit particies and/or rays. 

Atoms remain unchanged, though they may be rearranged. 2. Atoms are often converted into atoms of another eiement. 

Invoive oniy vaience eiectrons. 3. May invoive protons, neutrons, and eiectrons. 

Associated with smaii energy changes. 4. Associated with iarge energy changes. 

Marie Curie named the process by which materials emit rays radioactivity. The rays and particles that are emitted by radioactive materials are called radiation. Marie and Pierre Curie s work helped establish the field of nuclear chemistry. 

Alpha radiation is a stream of alpha particles (helium nuclei). The equations below describe what happens when radium-226 (whose nucleus contains 88 protons and 138 neutrons) emits an alpha particle. 

Notice that the sum of the mass numbers (superscripts) and the sum of the atomic numbers (subscripts) on each side of the arrow are equal, that is, the particles are balanced. When a radioactive nucleus undergoes alpha decay, the resulting nucleus has an atomic number that is lower by 2 and a mass number that is lower by 4. The change in atomic number changes the identity of the element. 

Solving Problems A Chemistry Handbook Chemistry Matter and Change 253 

What element is foraied when each of the following radioisotopes undergoes alpha decay Give the atomic number and mass number of the element. 

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The isotope boron-10 is used as a control for nuclear reactors, as a shield for nuclear radiation, and in instruments used for detecting neutrons. Boron nitride has remarkable properties and can be used to make a material as hard as diamond. The nitride also behaves like an electrical insulator but conducts heat like a metal. 

Alkylated aromatics have excellent low temperature fluidity and low pour points. The viscosity indexes are lower than most mineral oils. These materials are less volatile than comparably viscous mineral oils, and more stable to high temperatures, hydrolysis, and nuclear radiation. Oxidation stabihty depends strongly on the stmcture of the alkyl groups (10). However it is difficult to incorporate inhibitors and the lubrication properties of specific stmctures maybe poor. The alkylated aromatics also are compatible with mineral oils and systems designed for mineral oils (see Benzene Toulene Xylenes and ethylbenzene). ... 

Fig. 23. Nuclear radiation level gauge, using an Ohmart-type ceU stack.

These provide thin films of a soHd, or a combination of soHds, interposed between two moving surfaces to reduce friction and wear. They are coming into more general use for high temperatures, vacuum, nuclear radiation, aerospace, and other environments that prohibit use of oils and greases. 

Nuclear Radiation Effects. Components of a nuclear reactor system that require lubrication include control-rod drives, coolant circulating pumps or compressors, motor-operated valves, and fuel handling devices, and, of course, are exposed to varying amounts of ionising (14). 

Radiation dose limits at a disposal site boundary are specified by the NRC as 25 x 10 Sv/yr (25 mrem/yr), a small fraction of the average radiation exposure of a person in the United States of 360 x 10 /Sv/yr (360 mrem/yr). Protection against nuclear radiation is fully described elsewhere... 

Initially, DADC polymers were used in military aircraft for windows of fuel and deicer-fluid gauges and in glass-fiber laminates for wing reinforcements of B-17 bombers. Usage in impact-resistant, lightweight eyewear lenses has grown rapidly and is now the principal appHcation. Other uses include safety shields, filters for photographic and electronic equipment, transparent enclosures, equipment for office, laboratory, and hospital use, and for detection of nuclear radiation. 

CdTe is used ia iafrared optics (41), phosphors, elelctroluminescent devices, photocells, and as a detector for nuclear radiation (42). 

Ionization The process of adding electrons to, or removing electrons from, atoms or molecules, thereby creating ions. High temperatures, electrical discharges, and nuclear radiation can cause ionization. 

Mega-electronVolt nuclei, nuclear radiations MeV 1.60x10-13 1000 keV... 

Nuclear equation, 513 Nuclear masses, 521t Nuclear radiation. See Radioactivity Nuclear reactions biological effects, 527 equations, 513 fission, 523-526 fusion, 526-527,528 mass-energy relations, 520-523,... 

Neutron activation reactions have also been considered for mine detection. Here a radioactive element is produced in the mine which in the process of decay, emits nuclear radiation, either alpha or beta particles or yrays or two of these or all three in combination. For buried mines the penetrating 7iays are of most in-... 

B.9 An unstable atomic nucleus gives off nuclear radiation consisting of particles that have a mass of about 1.7 X 10 kg. The particles are attracted to a negatively charged plate. The radiation consists of what type of subatomic particle ... 

FIGURE 17.4 The effects of an electric field on nuclear radiation. The direction of deflection shows that a-rays are positively charged, p-rays negatively charged, and y-rays uncharged. 

Since Rutherford s work, scientists have identified other types of nuclear radiation. Some consist of rapidly moving particles, such as neutrons or protons. Others consist of rapidly moving antiparticles, particles with a mass equal to that of one of the subatomic particles but with an opposite charge. For example, the positron has the same mass as an electron but a positive charge it is denoted 3 or f e. When an antiparticle encounters its corresponding particle, both particles are annihilated and completely converted into energy. Table 17.1 summarizes the properties of particles commonly found in nuclear radiation. 

Alternative symbols are given for the particles often it is sufficient to use the simplest (the one on the right). Electron capture is not nuclear radiation but is included for completeness. 

The ability of nuclear radiation to eject electrons from atoms and ions can be used to measure its intensity. Becquerel first gauged the intensity of radiation by determining the degree to which it blackened a photographic film. The blackening results from the same redox processes as those of ordinary photography, such as... 

The protection of components against nuclear radiation is a critical factor in the design of nuclear-fission components.P CVD is used extensively in this area, particularly in the coating of nuclear fuel particles such as fissile U-235, U-233, and fertile Th-232 with pyrolytic carbon. The carbon is deposited in a fluidized-bed reactor (see Ch. 4). The coated particles are then processed into fuel rods which are assembled to form the fuel elements. 

As a high-energy particle passes through matter, it creates an ionization track that contains positive ions. These ions are chemically reactive because their bonds are weakened by the loss of bonding electrons. Even though each cation eventually recaptures an electron to return to electrical neutrality, many ions first undergo chemical reactions that are the source of the damage done by nuclear radiation. 

Because nuclear radiation varies considerably in energy, the potential to cause damage cannot be assessed simply by counting the number of emissions. The energy of emissions must also be taken into account. Furthermore, the three different t T)es of nuclear radiation affect human cells to different extents. When the amount, energy content, and t T)e of radiation are taken into account, the result is a measure of the effect of radiation on the human body. This is expressed using a unit called the rem. 

Different t T)es of body cells show different sensitivities to nuclear radiation. Cells that divide most rapidly tend to be most easily damaged. These include bone marrow, white blood cells, blood platelets, the lining of the gastrointestinal tract, and cells in the gonads. Consequently, the S3Tnptoms of radiation sickness include loss of blood functions and gastrointestinal distress. 

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