Actinium discovery

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). 

The discovery of two new elements started a frenetic race to find more. Actinium was soon unearthed (Debierne 1900) and many other substances were isolated from U and Th which also seemed to be new elements. One of these was discovered somewhat fortuitously. Several workers had noticed that the radioactivity of Th salts seemed to vary randomly with time and they noticed that the variation correlated with drafts in the lab, appearing to reflect a radioactive emanation which could be blown away from the surface of the Th. This Th-emanation was not attracted by charge and appeared to be a gas, °Rn, as it turns out, although Rutherford at first speculated that it was Th vapor. Rutherford swept some of the Th-emanation into a jar and repeatedly measured its ability to ionize air in order to assess its radioactivity. He was therefore the first to report an exponential decrease in radioactivity with time, and his 1900 paper on the subject introduced the familiar equation dN/dt = - iN, as well as the concept of half-lives (Rutherford 1900a). His measured half-life for the Th emanation of 60 seconds was remarkably close to our present assessment of 55.6 seconds for °Rn. 

The radioactive element is a silvery, shiny, soft metal that is chemically similar to calcium and barium. It is found in tiny amounts in uranium ores. Its radioactivity is a million times stronger that that of uranium. Famous history of discovery (in a shed). Initially used in cancer therapy. Fatal side effects. Small amounts are used in luminous dyes. Radium was of utmost importance for research into the atom. Today its reputation is rather shaky as its decay gives rise to the unpleasant radon (see earlier). In nuclear reactors, tiny amounts of actinium are formed from radium. 

Francium - the atomic number is 87 and the chemical symbol is Fr. The name derives from the country France , where the French physicist Marguerite Percy from the Curie Institute in Paris, France discovered it in 1939 in the alpha particle decay of actinium, Ac => He => Fr, which was known as actinium-K and has a half-life of 22 minutes. An earlier claim of discovery in 1930 with the element name Virginium was determined to be incorrect. A similar claim for discovery of the element with atomic number 87 and named moldavium was also determined to be incorrect. The longest half-life associated with this unstable element is 22 minute Fr. 

Marguerite Catherine Perey, an assistant to Marie Curie, is credited with the discovery of francium-223 in 1939. Perey discovered the sequence of radioactive decay of radium to actinium and then to several other unknown radioisotopes, one of which she identified as francium-223. Since half of her sample disappeared every 21 minutes, she did not have enough to continue her work, but a new element was discovered. 

It was first identified and named brevium, meaning brief, by Kasimir Fajans and O. H. Gohring in 1913 because of its extremely short half-life. In 1918 Otto Hahn (1879—1968) and Lise Meitner (1878-1968) independently discovered a new radioactive element that decayed from uranium into (actinium). Other researchers named it uranium X2. It was not until 1918 that researchers were able to identify independently more of the elements properties and declare it as the new element 91 that was then named protactinium. This is another case in which several researchers may have discovered the same element. Some references continue to give credit for protactinium s discovery to Frederich Soddy (1877—1956) and John A. Cranston (dates unknown), as well as to Hahn and Meitner. 

The chemistry of neptunium (jjNp) is somewhat similar to that of uranium (gjU) and plutonium (g4Pu), which immediately precede and follow it in the actinide series on the periodic table. The discovery of neptunium provided a solution to a puzzle as to the missing decay products of the thorium decay series, in which all the elements have mass numbers evenly divisible by four the elements in the uranium series have mass numbers divisible by four with a remainder of two. The actinium series elements have mass numbers divisible by four with a remainder of three. It was not until the neptunium series was discovered that a decay series with a mass number divisible by four and a remainder of one was found. The neptunium decay series proceeds as follows, starting with the isotope plutonium-241 Pu-24l—> Am-24l Np-237 Pa-233 U-233 Th-229 Ra-225 Ac-225 Fr-221 At-217 Bi-213 Ti-209 Pb-209 Bi-209. 

In 1949, about half a century after the discovery of actinium, the International Rare Metals Refinery, Inc. produced it industrially (134). It is about 150 times as active as radium and is a valuable source of neu-... 

Sir Alexander Fleck, 1889—. Author of many research papers on the radioactive isotopes. He proved the inseparability of uranium Xi and radioaetinium from thorium, of thorium B and actinium B from lead, of mesothorium 2 from actinium, of radium E from bismuth, and of radium A from polonium, and confirmed the discovery of uranium X3 by Faj ans and O. H. Gohring. Chairman of Imperial Chemical Industries, Ltd. See also ref. (1S7). 

The actual discovery was made by Mile. Marguerite Perey at the Curie Institute in Paris. In 1939 she purified an actinium preparation by removing all the known decay products of this element. In her preparation she observed a rapid rise in beta activity which could not be due to any known substance. She was able to show that, while most of the actinium formed radioactinium, an isotope of thorium, by beta emission, 1.2 0.1 per cent of the disintegration of actinium occurred by alpha emission and gave rise to a new element, which she provisionally called actinium K, symbol AcK (35, 36). This decayed rapidly by beta emission to produce AcX, an isotope of radium, which was also formed by alpha emission from radioactinium. Thus AcK, with its short half-life, had been missed previously because its disintegration gave the same product as that from the more plentiful radioactinium. 

Presently. 24 isotopes of actinium, with mass numbers ranging from 207 to 2.30, have been identified. All are radioactive. One year after the discovery of polonium and radinm by the Curies, A. Debierne found an unidentified radioactive substance in the residue after treatment of pitchblende. Debierne named the new material actinium after the Greek word for ray. F. Giesel, independently in 1902, also found a radioactive material in the rare-earth extracts of pitchblende. He named... 

O. Hahn and L. Meitner, Die Muttersub-stanz des Actiniums, Physikalische Zeit-schrift 19 (1918) 208-18 R. L. Sime, The Discovery of Protactinium, Journal of Chemical Education 63 (1986) 653-57. 

The element francium is named for the country of France and its most stable isotope is known as actinium K. Dimitri Mendeleev assigned it the name eka-cesium prior to its actual discovery, although at this time it was also known as russium, virginium, and moldavium. Marguerite Perey, a one-time assistant of Marie Curie, discovered francium in 1939. It is not found in its elemental state and less than one ounce is thought to exist in Earth s crust at any one time. 

Up till a few years ago four elements were still missing from the roll-call, in fact 43, 61, 85, and 87, although their discovery had been announced repeatedly but always incorrectly. These elements have now all been prepared artificially and they have been found to be radioactive, while there are also grounds for assuming that stable isotopes of these elements cannot exist. These elements, if they have ever existed, have, at least as far as the first two are concerned, very probably died out on earth long ago, just as radium (half-life 1590 years) would also have remained unknown to us if it had not continually originated afresh from the extremely slowly decaying uranium (half-life 4.49 io9 years). The presence of 87 in extremely small quantities in the decomposition products of actinium was first dis-... 

The earliest discovery of actinium is attributed to A. Debieme in 1899, with F. Giesel also identifying and isolating the element in 1902. The name actinium is derived from the Greek word for ray, aktinos , which acknowledges the radioactive behavior of the element. 

Uranium Y is isotopic with uranium X, and is therefore tetravalent. Since it gi es off -rays, it is unlikely, according to the Group-displacement Law, that it will change directly into trivalent actinium there should be an intermediate a-ray product. This conclusion was cozi-firmed by the discovery of eka-tantalum or protoactiniuni, which is the immediate parent of actinium. ... 

Actinium was discovered a second time in 1902. German chemist Friedrich O. Giesel (1852-1927) had not heard of Debierne s earlier discovery. Giesel suggested the name emanium, from the word emanation, which means to give off rays. Debierne s name was adopted, however, because he discovered actinium first. 

The name comes from the Greek aktis, meaning beam or ray. It was discovered by Andre-Louis Debierne (1874-1949) in 1899 and independently by Fritz Giesel (1852-1927) in 1902. It exists in very small quantities in association with uranium ores. Actinium has few uses outside the laboratory, but its discovery was important for the development of chemistry and physics, as it was one of the materials used to study radioactive decay, since it breaks down into thorium, radium, radon, bismuth, polonium, and isotopes of lead. 

Actinium and the actinide elements (thorium, etc.) also are listed separately at the bottom. Each actinide element is somewhat similar to actinium and to the lanthanide element with which it is paired. The discovery of hafnium (Hf) in 1923 and rhenium (Re) in 1925 completed the Periodic Table through uranium except for four blank spaces. 

All these new discoveries, of course, verified Seaborg s theory, and the transuranium elements, along with thorium, protactinium and uranium, are now called the actinide elements. They all fit in the Periodic Table between actinium and the element eka-hafnium. Eka-hafnium is the tentative name given to the undiscovered element with the atomic number 104 which lies directly below hafnium in the Periodic Table and which is expected to have chemical properties similar to those of hafnium. 

The last discovery of an alkali metal occurred almost 80 years later. In 1939, Parisian physicist Marguerite Perey (1909-75) observed an unusual rate of radioactive decay in a sample of a salt of actinium (element 89). She managed to isolate the new element, showed that it was an alkali metal, and named it francium in honor of her native country, France. Because francium s longest-lived isotope has a half-life of only 21 minutes, francium is the rarest element below element 98 in the periodic table, which explains why francium was discovered much later than the other radioactive elements in that part of the table. 

After the discovery of uranium radioactivity by Henri Becquerel in 1896, uranium ores were used primarily as a source of radioactive decay products such as Ra. With the discovery of nuclear fission by Otto Hahn and Fritz Strassman in 1938, uranium became extremely important as a source of nuclear energy. Hahn and Strassman made the experimental discovery Lise Meitner and Otto Frisch provided the theoretical explanation. Enrichment of the spontaneous fissioning isotope U in uranium targets led to the development of the atomic bomb, and subsequently to the production of nuclear-generated electrical power. There are considerable amounts of uranium in nuclear waste throughout the world, see also Actinium Berkelium Einsteinium Fermium Lawrencium Mendelevium Neptunium Nobelium Plutonium Protactinium Rutherfordium Thorium. 

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