Radium atomic properties

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. 

Soon after Becquerel s discovery of uranium s radioactivity, Marie Sklodowska Curie (1867—1934), also working in France, studied the radioactivity of thorium (Th) and began to search systematically for new radioactive elements. She showed that the radioactivity of uranium was an atomic property— that is, its radioactivity was proportional to the amount of the element present and was not related to any particular compound. Her experiments indicated that other radioactive elements were probably also present in certain uranium samples. With painstaking technique, she and her husband Pierre Curie (1859-1906) separated the element radium (Ra) from uranium ore and found that it is more than one million times more radioactive than uranium. In 1903, Marie and Pierre Curie shared the Nobel Prize in physics with Henri Becquerel for their discovery of radioactivity. After Pierre died. 

Marie Sklodowska Curie, born in Warsaw, Poland, began her doctoral work with Henri Becquerel soon after he discovered the spontaneous radiation emitted by uranium salts.She found this radiation to be an atomic property and coined the word radioactivity for it. In 1903 the Curies and Becquerel were awarded the Nobel Prize in physics for their discovery of radioactivity.Three years later, Pierre Curie was killed in a carriage accident.Marie Curie continued their work on radium and in 1911 was awarded the Nobel Prize in chemistry for the discovery of polonium and radium and the isolation of pure radium metal.This was the first time a scientist had received two Nobel awards. (Since then two others have been so honored.)... 

These two kinds of lead are now known to be isotopes, or inseparable elements which belong in the same space in the periodic table and yet differ in atomic weight and in radioactive properties. According to Frederick Soddy, the first clear recognition of isotopes as chemically inseparable substances was that of H. N. McCoy and W. H. Ross in 1907 (75,107). Strictly speaking, the science of radioactivity has revealed only five naturally occurring new elements with distinctive physical and chemical properties polonium, thoron, radium, actinium, and uranium X2. All the other natural radioactive elements share previously occupied places in the periodic table. 

Uranium-238 emits an alpha particle to become an isotope of thorium. This unstable element emits a beta particle to become the element now known as Protactinium (Pa), which then emits another beta particle to become an isotope of uranium. This chain proceeds through another isotope of thorium, through radium, radon, polonium, bismuth, thallium and lead. The final product is lead-206. The series that starts with thorium-232 ends with lead-208. Soddy was able to isolate the different lead isotopes in high enough purity to demonstrate using chemical techniques that the atomic weights of two samples of lead with identical chemical and spectroscopic properties had different atomic weights. The final picture of these elements reveals that there are several isotopes for each of them. 

Elements 43, Masurium 61, Illinium 84, Polonium or Radium F 89, Actinium 91, Uranium Xs do not appear in the atomic weight tables. Although their existence has been indicated by means of X-rays or radioactive properties, they have not been isolated in amounts to allow of atomic weight determination. 

The Bq is a minute measure of radioactivity and any sizeable amount of radioactive material will contain very many atoms and thus emit considerable amounts (TBq or GBq) of radiation. Another popular unit of decay is the curie, a non-Sl unit (historically calculated from the disintegrations of radium) which is equivalent to 37 x 10 Bq. Importantly, radioactivity decays exponentially, where a population of atoms in a sample will have a characteristic half-life (fi/2). The half-life is the key parameter when considering radioactivity and associated safety of radioisotopes, where fi/2 represents the time taken for the radioactivity to fall to a half the recorded level, as illustrated in Figure 10.4. Half-lives and associated properties of common radioactive isotopes are given in Table 10.2. 

After helium and argon had been discovered the existence of neon, krypton, xenon, and radon was clearly indicated by the periodic law, and the search for these elements in air led to the discovery of the first three of them radon was then discovered during the investigation of the properties of radium and other radioactive substances. While studying the relation between atomic structure and the periodic law Niels Bohr pointed out that element 72 would be expected to be similar in its properties to zirconium. G. von Hevesy and D. Coster were led by this observation to examine ores of zirconium and to discover the missing element which they named hafnium. 

The Seventh Period Elements. The remaining six places in the seventh and last period are filled with atoms which, apart from their pronounced radio-active properties, introduce nothing new in the way of electron arrangement. The first two elements, eka-caesium and radium, have respectively one and two electrons in a new seventh outer layer, while the four remaining elements fall in line with the first four transition elements of periods four and five. It would thus seem that the four electrons concerned then take their places in the sixth layer, the outer two persisting in the last four of the known elements. Thus ... 

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