Gamma particles

A stream of alpha particles is sometimes called an alpha ray. A stream of beta particles is called a beta ray. A gamma ray is composed of a stream of gamma particles. 

The emission of a gamma particle causes no change in the charge or mass number of the original particle. (It does cause a change in its internal energy, however.) For example,... 

The same oSn isotope is produced, but it has a lower energy after the emission of the gamma particle. 

EXAMPLE 22.7. When a 2 1 nucleus disintegrates, the following series of alpha and bela particles is emitted alpha, beta, beta, alpha, alpha, alpha, alpha, alpha, beta, alpha, beta, beta, beta, alpha. (Since emission of gamma particles accompanies practically every disintegration and since gamma particles do not change the atomic number or mass number of an isotope, they are not listed.) Show that each isotope produced has a mass number that differs from 238 by some multiple of 4. 

In each case, the final product must differ from the original parent by some multiple of 4 mass numbers. For example, the 208Pb differs in mass number from 232Th by 24 = 4 x 6. There must have been six alpha particles emitted in this decay scries, with a reduction of four mass numbers each. (The beta and gamma particles emitted do not affect the mass number.)... 

Ans. (a) The mass number changes by 28 units in this series, corresponding to seven alpha particles (7x4 = 28). (b) The seven alpha particles emitted would have reduced the atomic number by 14 units if no beta particles had been emitted since the atomic number is reduced by only 10 units, four (14 - 10) beta particles are also emitted, (c) It is impossible to tell from these data alone what the order of emission is. (d) It is impossible to tell the number of gamma particles emitted, since emission of a gamma particle does not change either the mass number or the atomic number. 

The work by Chen et al. also resulted in no measurable incorporation with particle diameters of 0.05 and 0.02 pm gamma alumina in copper [31]. When the 0.02 pm gamma particles were calcined to obtain a mix of gamma and alpha alumina, codeposition increased to 2.9 vol.%, under the same codeposition conditions. Furthermore, when the 0.02 pm gamma powders were completely converted to the alpha phase of alumina, incorporation rose to 3.3 vol.% [31]-... 

When a slow neutron is captured by the nucleus of element X, another isotope of the same element is instantaneously formed, in an excited state because of the impact (labelled compound nucleus in Figure 2.13), which then de-excites by the emission of a gamma particle (and possibly other particles) from the nucleus to produce a radioactive nucleus. For example, when 23Na captures a neutron (signified by on, since neutrons have a mass of one unit, but no electrical charge), it becomes the radioactive nucleus 24Na, as follows ... 

Gamma particle Energetic photon (particle of light) originating from the nucleus of an atom produced when a neutron or proton drops from a high energy level to a lower energy level. 

Radioactivity results when some part of an atom is unstable. The instability exists because the orbital electrons or the nucleus contain too much energy. Radioactive atoms are called radionuclides. They release excess energy by emitting radiation. The type of radiation released (alpha, beta, or gamma particles) may be more or less hazardous to humans, depending on the location of the radioactive materials. Exposure to radioactive materials outside the body poses external hazards. Radioactive materials may also be hazardous when ingested, inhaled, or injected and thus pose internal hazards. The sections below describe the characteristics of radiation particles as external or internal hazards and as they may be encountered after a terrorist attack. Chapter 3 provides additional details and addresses health effects associated with exposure to radiation. 

Other types of radiation exist, but for the purposes of simplicity, only alpha, beta, and gamma particles are discussed. The term particle is used even though radiation may be defined differently under other applications. 

Measurement of radioactiviry, as an analytical tool became possible after the discoveries of A.H.Becquerel(uranium radiation 1896), Pi re Marie Curie (polonium radium in 1898), Sir E. Rutherford (identification of Becquerel rays as consisting of alpha-, beta and gamma-particles) and of F.Soddy(phenomenon of nuclear disintegration, in 1902)... 

Compton, photo, and pair electrons produced by gamma particles in the counter wall and in the gas. 

Naturally radioactive materials (found in the earth s crust) give off alpha, beta, or gamma particles. Alpha particles are Helium nuclei, beta particles are electrons, and gamma particles are high energy photons. 

Superscripts and subscripts may be used with the Greek letters that represent alpha, beta, and gamma particles. Eor example, an alpha particle can be represented by the Greek letter alpha (a) or the symbol " He. In either case, the subscript can be used or omitted. With the Greek letter, the superscript is also... 

The emission of a gamma particle does not change the atomic number or the mass number of the parent isotope because the gamma particle has zero charge and zero mass number. For example, the emission of a gamma particle from oSn yields a lower-energy form of the same isotope ... 

Thus, in gamma particle emission, the identity of the element does not change. 

Show that the emission of a gamma particle does not change the atomic number or the mass number of the parent isotope. 

Because the superscript and the subscript on the symbol for the gamma particle are both zero, the superscript and the subscript of the daughter isotope must be the same as those of the parent isotope for the mass numbers and charges to balance. ... 

The daughters of most radioactive isotopes with very high atomic numbers will themselves disintegrate, and a whole series of disintegrations takes place. All the isotopes involved form a radioactive series. For example, loses seven alpha particles and four beta particles (as well as some gamma particles) as it... 

The mass number changes by 4 when an alpha particle is emitted but does not change at all when a beta or a gamma particle is emitted. Therefore, the mass numbers of all the isotopes in a given series differ from one another by some integral multiple (0, 1, 2,...) of 4. Because of this fact, there are four different series. One of them has mass numbers evenly divisible by 4 it is called the 4 series. In another saies, all of the mass numbers exceed a multiple of 4 by 1 it is called the 4 + 1 sales. Similarly, the other two series are the 4 + 2 and the 4 + 3 series. The disintegrations in the 4 , 4 + 1, and 4 + 3 series are shown in Figure 21.2. 

Radium was discovered by Marie Curie (1867-1934) in pitchblende, a uranium ore. Radium is produced from a series of disintegrations, starting with and each producing an alpha particle or a beta particle (and possibly a gamma particle). Without looking at any figure or table, but using the mass number of l Ra, deduce how many alpha particles have been emitted from to produce this isotope of radium. 

The emission of an alpha particle lowers the mass number of the daughter isotope by 4 the emission of a beta particle or a gamma particle produces no loss... 

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