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Origin and Properties of Radioactivity

Radioactivity results from the spontaneous nuclear disintegration of unstable isotopes. The hydrogen nucleus, consisting of a proton, is represented as JH. Two additional forms of the hydrogen nucleus contain one and two neutrons they are represented by 2H and jH. These isotopes of hydrogen are commonly called deuterium and tritium, respectively. All isotopes of [Pg.171]

The stability of a nucleus depends on the ratio of neutrons to protons. Some nuclei are unstable and undergo spontaneous nuclear disintegration accompanied by emission of particles. Unstable isotopes of this type are called radioisotopes. Three main types of radiation are emitted during nuclear decay a particles, j8 particles, and y rays. The a particle, a helium nucleus, is emitted only by elements of mass number greater than 140. These elements are seldom used in biochemical research. [Pg.172]

A few radioisotopes of biochemical significance are y emitters. Emission of a y ray (a photon of electromagnetic radiation) is often a secondary process occurring after the initial decay by /3 emission. The disintegration of the isotope 131I is an example of this multistep process. [Pg.172]

Each radioisotope emits y rays of a distinct energy, which can be measured for identification of the isotope. [Pg.172]

The spontaneous disintegration of a nucleus is a first-order kinetic process. That is, the rate of radioactive decay of TV atoms (—dN/dt, the change of TV with time, t) is proportional to the number of radioactive atoms present (Equation 6.4). [Pg.172]


Indeed, the Theosophical infusion of matter with life, and the ability of life force and will to effect the changes in matter demanded by spiritual alchemy and occult chemistry, seemed to find some support from the newly discovered phenomenon of radiation. Besant s On the Watch-Tower column, for instance, noted with excitement an article on the origin of life by Butler Burke published in the Daily Chronicle in 1905. There, Burke noted that radium may be that state of matter that separates, or perhaps unites, the organic and the inorganic worlds, and that radioactivity endows matter with some of the properties of organic matter (quoted in [Besant] 1905a, 481). [Pg.89]

Marie (NLP 1903, NLC 1911 ) and Pierre (NLP 1903 ) Curie took up further study of Becquerel s discovery. In their studies, they made use of instrumental apparatus, designed by Pierre Curie and his brother, to measure the uranium emanations based on the fact that these emanations turn air into a conductor of electricity. In 1898, they tested an ore named pitchblende from which the element uranium was extracted and found that the electric current produced by the pitchblende in their measuring instrument was much stronger than that produced by pure uranium. They then undertook the herculean task of isolating demonstrable amounts of two new radioactive elements, polonium and radium, from the pitchblende. In their publications, they first introduced the term radio-activity to describe the phenomenon originally discovered by Becquerel. After P. Curie s early death, M. Curie did recognize that radioactive decay (radioactivity) is an atomic property. Further understanding of radioactivity awaited the contributions of E. Rutherford. [Pg.5]

The period t = 1/fc is sometimes referred to as the natural lifetime of species A. During time t, the concentration of A decreases to He of its original value. A second period, from r = t to f = 2t, produces an equivalent fractional decrease in concentration to 1/e of the value at the beginning of the second interval, which is (1/e) of [AJo- A more familiar example of this property of exponentials is found in the half-life tu2 of radionuclides. During a period t n, half of the atoms in a sample of a radioactive element decay to products a second period of t i2 reduces the amount of the element to one quarter of its original number, and so on for succeeding periods. Regardless of the time interval chosen, equal elapsed times produce equal fractional decreases in reactant concentration for a first-order process. [Pg.882]

By 1910 proximately 40 differrait chemical species had been id tified through their chemical nature, the properties of their radiation, and their characteristic half-lives. The study of the generic relationships in the decay of the radioactive species showed that the radioelements could be divided into three distinct series. Two of these originated in uranium and the third in thorium. B. Boltwood found that all three of the series ded in the same... [Pg.3]

The actinides are a row of radioactive elements from thorium to lawrencium. They were not always separated into their own row in the periodic table. Originally, the actinides were located within the d-block following actinium. In 1944, Glenn Seaborg proposed a reorganization of the periodic chart to reflect what he knew about the chemistry of the actinide elements. He placed the actinide series elements in their own row directly below the lanthanide series. Seaborg had played a major role in the discovery of plutonium in 1941. His reorganization of the periodic table made it possible for him and his coworkers to predict the properties of possible new elements and facilitated the synthesis of nine additional transuranium elements. [Pg.921]

Bohr learned about radiochemistry from de Hevesy. He began to see connections with his electron-theory work. His sudden burst of intuitions then was spectacular. He realized in the space of a few weeks that radioactive properties originated in the atomic nucleus but chemical properties depended primarily on the number and distribution of electrons. He realized—the idea was wild but happened to be true—that since the electrons determined the chemistry and the total positive charge of the nucleus determined the number of electrons, an element s position on the periodic table of the elements was exactly the nuclear charge (or atomic number ) hydrogen first with a nuclear charge of 1, then helium with a nuclear charge of 2 and so on up to uranium at 92. [Pg.67]


See other pages where Origin and Properties of Radioactivity is mentioned: [Pg.171]    [Pg.173]    [Pg.175]    [Pg.6]    [Pg.171]    [Pg.15]    [Pg.179]    [Pg.171]    [Pg.173]    [Pg.175]    [Pg.6]    [Pg.171]    [Pg.15]    [Pg.179]    [Pg.8]    [Pg.81]    [Pg.1184]    [Pg.18]    [Pg.205]    [Pg.26]    [Pg.206]    [Pg.128]    [Pg.101]    [Pg.93]    [Pg.375]    [Pg.170]    [Pg.526]    [Pg.125]    [Pg.164]    [Pg.448]    [Pg.22]    [Pg.479]    [Pg.848]    [Pg.382]    [Pg.4]    [Pg.65]    [Pg.589]    [Pg.866]    [Pg.4]    [Pg.683]    [Pg.687]    [Pg.675]    [Pg.679]    [Pg.73]    [Pg.168]    [Pg.724]    [Pg.521]    [Pg.670]    [Pg.145]    [Pg.343]    [Pg.4]   


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