ALPHA a PARTICLES

Alpha (a) particles are identical to the nuclei of helium atoms ( He). Their speed is approximately 1/10 of the speed of light. Since they are 2+ charged particles, they are symbolized as A - e2+. They are deflected by electric and magnetic fields because of their positive charge. 

As they penetrate through matter, alpha particles produce large amount of ions, but their penetrating power is so low that they can easily be stopped by a sheet of paper. 

The nucleus of an atom undergoing an alpha decay loses He2+ particles that is, it emits two protons and two neutrons. Therefore, there will be a decrease of two in the atomic number and four in the atomic mass number of that nucleus. 

For instance, if an g2CI isotope radiates one alpha particle, the nuclear equation can be expressed as shown below. 

The atomic number and atomic mass Radioactive 2ggTh isotope emits one a particle and transmutes to atom X. Find the 

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Figure 3.1 James Chadwick used the apparatus depicted above to discover the neutron. The poionium source emits alpha (a) particles. The particles strike a sample of beryllium, resulting in the emission of a neutron (n ). The ejected neutrons hit the target material—paraffin, for instance—and eject a proton that is recorded by the detection device.

The third experiment that is crucial to understanding atomic structure was carried out by Ernest Rutherford in 1911 and is known as Rutherford s experiment. It consists of bombarding a thin metal foil with alpha (a) particles. Thin foils of metals, especially gold, can be made so thin that the thickness of the foil represents only a few atomic diameters. The experiment is shown diagrammatically in Figure 1.2. 

Alpha (a) particles An a particle is composed of two protons and two neutrons, with a charge of +2 essentially, it is a helium nucleus without orbital electrons. Alpha particles usually originate from the nuclear decay of radionuclides of atomic number >82, and are detected in samples containing U, Th, or Ra. Alpha particles react strongly with matter and consequently produce large numbers of ions per unit... 

Alpha (a) particles Helium nuclei (2 He). A common by-product of the radioactive decay of primordial radionuclides. 

Rutherford s work involved the use of alpha (a) particles, a type of emission previously observed to be given off by a number of naturally occurring radioactive elements, including radium, polonium, and radon. Rutherford knew that alpha particles are about 7000 times more massive than electrons and that they have a positive charge that is twice the magnitude of the charge on an electron, but opposite in sign. 

An alpha (a) particle j 1 (2I lo2+) is a helium nucleus, but the +2 charge is not used in writing nuclear equations. 

Alpha decay is nuclear decomposition such that one of the products of the reaction is an alpha (a) particle, 4He. In an example of alpha decay, radium-222 decomposes to form radon-218 plus an alpha particle ... 

While Thomson and others were busy studying electrical phenomena, Henri Becquerel discovered a new phenomenon—radiation. (We will discuss radiation in more detail in Chapter 5.) The study of this new type of high-energy emission from materials was the principal focus of Ernest Rutherford. Rutherford s initial work discovered two new types of particles associated with the high-energy emissions, the alpha (a) particle and the beta ((3). These are now known to be a helium nucleus and an electron, respectively (more on this in Chapter 5). 

Alpha (a) particle emission, or alpha decay, involves the loss of one alpha particle. An a particle is a helium nucleus, He, composed of two protons and two neutrons. Since it has no electrons, an alpha particle carries a charge of +2. 

Alpha (a) particle It is a double positive charge carrying helium nucleus He2+) released spontaneously from a high-atomic mass radioactive element. It has low penetration power and can be stopped by a thin sheet of paper or a layer of air. Has no external hazards has internal hazards. 

Carboranes in Boron Neutron Capture Therapy of Cancer (B7YC2). The stable isotope of boron, B (19.8% natural abundance), is very effective as a neutron capture agent with the effective nuclear cross section of 3837 bams, while the "B nucleus is incapable of undergoing a BNC reaction. Therefore, the B-emiched carborane and borane-substituted biomolecules and dmgs are selectively dehvered to the cancer cells in the human body and then the tumor-localized B nucleii are bombarded with either thermal or epithermal neutrons that results in a fission reaction producing the high energy alpha (a) particles as shown in equation (2). 

Alloy steel a form of steel containing carbon plus other metals such as chromium, cobalt, manganese, and molybdenum. (20.2) Alpha (a) particle a helium nucleus. (21.1)... 

Alpha Decay. To achieve stable configurations, heavy elements, particularly those with atomic numbers above 70, may shed some of their nuclear mass by emitting a two-proton, two-neutron fragment identifiable after emission as a helium nucleus. Because nuclear radiations were observed before their identity was known, this fragment was called an alpha (a ) particle, and its emission is termed a-decay. Alpha particles are relatively large in mass, interact strongly with matter, but are absorbed by as little as a sheet of paper. However, because they are so heavy, even with low velocity. 

Alpha (a) particle A helium ion with a 2 -I- charge an assembly of two protons and two neutrons. 

The main ionising radiations are alpha (a) particles, beta ((3) particles,... 

Alpha decay involves the loss of a particle equivalent to a helium nucleus. Alpha (a) particles, being large and positively charged, do not penetrate far in living tissue, but they do cause ionization damage and this makes them generally unsuitable for tracer studies. 

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