Curie Radioactives

The guiding principle that was decisive in the choice of Rontgen is also true for Antoine H. Bec-guerel (1852-1908 Nobel Prize for physics 1903 together with Pierre and Marie Curie). His discovery of radioactivity was not only the basis for the unraveling of new elements (radium and polonium by the Curies). Radioactivity and its phenomena became a universal tool that provided succeeding chemists and physicists with insight into the world of atoms. 

The name radioactivity was coined two years later (in 1898) by Marie Curie. Radioactivity is the spontaneous emission of particles and/or rays from the nucleus of an atom. Elements having this property are said to be radioactive. 

Plot the equation A curies (radioactivity unit) and X 25 years. 

Poland, native country of Mme. Curie) Polonium, also called Radium F, was the first element discovered by Mme. Curie in 1898 while seeking the cause of radioactivity of pitchblend from Joachimsthal, Bohemia. The electroscope showed it separating with bismuth. 

In 1896, only a few months after Roentgen aimounced the observation of x-rays, Becquerel reported the additional observation of penetrating radiation emitted from certain natural materials, a phenomenon that Marie Curie would later name radioactivity. This phenomenon had a much less glamorous development. Over a three-year period, Becquerel pubHshed three articles, decided there was Htfle else to learn about it, and went on to the study... 

The activity of a sample, source or contaminated material is the rate at which radioactive disintegrations are taking place. The initial term, named by Madam Curie for her husband was, the Curie (Table 8.3-1). The modem unit is the Becquerel named after the discoverer of... 

Curie (Ci) A unit of radioactivity, related to the emission from 1 g of radium, it is equal to 3.7 x 10 disintegrations per gram per second. This unit has been replaced by the Becquerel (Bq) 1... 

The isolation and identification of 4 radioactive elements in minute amounts took place at the turn of the century, and in each case the insight provided by the periodic classification into the predicted chemical properties of these elements proved invaluable. Marie Curie identified polonium in 1898 and, later in the same year working with Pierre Curie, isolated radium. Actinium followed in 1899 (A. Debierne) and the heaviest noble gas, radon, in 1900 (F. E. Dorn). Details will be found in later chapters which also recount the discoveries made in the present century of protactinium (O. Hahn and Lise Meitner, 1917), hafnium (D. Coster and G. von Hevesey, 1923), rhenium (W. Noddack, Ida Tacke and O. Berg, 1925), technetium (C. Perrier and E. Segre, 1937), francium (Marguerite Percy, 1939) and promethium (J. A. Marinsky, L. E. Glendenin and C. D. Coryell, 1945). 

Radium, the last element in the group, was isolated in trace amounts as the chloride by P. and M. Curie in 1898 after their historic processing of tonnes of pitchblende. It was named by Mme Curie in allusion to its radioactivity, a word also coined by her (Latin radius, a ray) the element itself was isolated electrolytically via an amalgam by M. Curie and A. Debieme in 1910 and its compounds give a carmine-red flame test. 

F. Joliot and Irene Joliot-Curie (Paris) synthesis of new radioactive elements. 

Curie chose for her dissertation research the new topic of uranium rays, a phenomenon that had only recently been observed by Henri Becqiierel. The mystery was the source of the energy that allowed uranium salts to expose even covered photographic plates. Curie s first efforts in the field were systematic examinations of numerous salts to determine which salts might emit rays similar to those of Becquerel s uranium. After discovering that both thorium and uranium were sources of this radiation. Curie proposed the term radioactive to replace uranium rays. She also discovered that the intensity of the emissions depended not on the chemical... 

Although the Curies noted that one equivalent gram of radium released one hundred calorics of heat per hour, they were uninterested in the practical implications of this, as they were both devoted to pure scientific discovery. During their work with pitchblende in 1898, the Curies discovered two new radioactive elements, which they named polonium (in honor of Marie s homeland) and radium. By 1902 they had isolated a pure radium salt and made the first atomic weight determination. 

The first radioactive isotopes to be made in the laboratory were prepared in 1934 by Irene Curie and her husband, Frederic Joliot They achieved this by bombarding certain stable isotopes with high-energy alpha particles. One reaction was... 

Marie and Irene Curie, and their husbands, Pierre Curie and Frederic Joliot. Marie Curie (1867-1934) was born Maria Sklodowska in Warsaw, Poland, then a part of the Russian empire. In 1891 she emigrated to Paris to study at the Sorbonne, where she met and married a French physicist, Pierre Curie (1859-1906). The Curies were associates of Henri Becquerel, the man who discovered that uranium salts are radioactive. They showed that thorium, like uranium, is radioactive and that the amount of radiation emitted is directly proportional to the amount of uranium or thorium in the sample. 

In 1898, Marie and Pierre Curie isolated two new radioactive elements, which they named radium and polonium. To obtain a few milligrams of these elements, they started with several tons of pitchblende ore and carried out a long series of tedious separations. Their work was done in a poorly equipped, unheated shed where the temperature reached 6°C (43°F) in winter. Four years later, in 1902, Marie determined the atomic mass of radium to within 0.5%, working with a tiny sample. 

In 1903, the Curies received the Nobel Prize in physics (with Becquerel) for the discovery of radioactivity. Three years later, Pierre Curie died at the age of 46, the victim of a tragic accident. Fie stepped from behind a carriage in a busy Paris street and was run down by a horse-driven truck. That same year, Marie became the first woman instructor at the Sorbonne. In 1911, she won the Nobel Prize in chemistry for the discovery of radium and polonium, thereby becoming the first person to win two Nobel Prizes. 

In 1921, Irene Curie (1897-1956) began research at the Radium Institute. Five years later she married Frederic Joliot (1900-1958). a brilliant young physicist who was also an assistant at the Institute. In 1931, they began a research program in nuclear chemistry that led to several important discoveries and at least one near miss. The Joliot-Curies were the first to demonstrate induced radioactivity. They also discovered the positron, a particle that scientists had been seeking for many years. They narrowly missed finding another, more fundamental particle, the neutron. That honor went to James Chadwick in England. In 1935,... 

Curie (unit) Radiation corresponding to the radioactive decay of3.700 X 1010 atoms/s, 518 Curie, Irene, 517 Curie, Marie, 248,517 Curie, Pierre, 517 Current flow, 496... 

In 1896, the French scientist Fienri Becquerel happened to store a sample of uranium oxide in a drawer that contained some photographic plates (Fig. 17.2). He was astonished to find that the uranium compound darkened the plates even though they were covered with an opaque material. Becquerel realized that the uranium compound must give off some kind of radiation. Marie Sklodowska Curie (Fig. 17.3), a young Polish doctoral student, showed that the radiation, which she called radioactivity, was emitted by uranium regardless of the compound in which it was found. She concluded that the source must be the uranium atoms themselves. Together with her husband, Pierre, she went on to show that thorium, radium, and polonium are also radioactive. 

The discoveries of Becquerel, Curie, and Rutherford and Rutherford s later development of the nuclear model of the atom (Section B) showed that radioactivity is produced by nuclear decay, the partial breakup of a nucleus. The change in the composition of a nucleus is called a nuclear reaction. Recall from Section B that nuclei are composed of protons and neutrons that are collectively called nucleons a specific nucleus with a given atomic number and mass number is called a nuclide. Thus, H, 2H, and lhO are three different nuclides the first two being isotopes of the same element. Nuclei that change their structure spontaneously and emit radiation are called radioactive. Often the result is a different nuclide. 

The activity of a certain radioactive source is 5.3 X 103 Bq. Express this activity in curies. 

A certain Geiger counter is known to respond to only 1 of every 1000 radiation events from a sample. Calculate the activity of each radioactive source in curies, given the following data (a) 591 clicks in 100. s (b) 2.7 X 104 clicks in 1.5 h ... 

Polonium, completing the elements of Group 16, is radioactive and one of the rarest naturally occurring elements (about 3 x 10 " % of the Earth s crust). The main natural source of polonium is uranium ores, which contain about lO g of Po per ton. The isotope 210-Po, occurring in uranium (and also thorium) minerals as an intermediate in the radioactive decay series, was discovered by M. S. Curie in 1898. 

Curie P, Curie M (1898) Sur une nouvelle substance radioactive, contenue dans la pechblende. Comptes Rendus de Seances de I academie de Sciences 127 175-178... 

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