Francium properties

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 alkali metals form a homogeneous group of extremely reactive elements which illustrate well the similarities and trends to be expected from the periodic classification, as discussed in Chapter 2. Their physical and chemical properties are readily interpreted in terms of their simple electronic configuration, ns, and for this reason they have been extensively studied by the full range of experimental and theoretical techniques. Compounds of sodium and potassium have been known from ancient times and both elements are essential for animal life. They are also major items of trade, commerce and chemical industry. Lithium was first recognized as a separate element at the beginning of the nineteenth eentury but did not assume major industrial importance until about 40 y ago. Rubidium and caesium are of considerable academic interest but so far have few industrial applications. Francium, the elusive element 87, has only fleeting existence in nature due to its very short radioactive half-life, and this delayed its discovery until 1939. 

C08-0122. From its location in the periodic table, predict some of the physical and chemical properties of francium. What element does it most closely resemble ... 

Not a great deal is known about francium s properties, but some measurements of its most stable isotope have been made. Its melting point is 27°C and its boiling point is 677°C, but its density is unknown. It is assumed to have a +1 oxidation state (similar to all the other alkali metals)... 

The failure to discover francium earlier is easy to understand when it is remembered that the half-life of the longest lived isotope is only 21 minutes. This gives the element the distinction of being the most unstable to radioactive disintegration of all elements up to number 98 (38). It is also noteworthy that this is the only element in the group discussed in this chapter which was not discovered by artificial preparation in the laboratory. Nevertheless, the rarity of actinium in nature is so great that this element is best prepared artificially when its properties or those of its daughter elements are to be studied. 

Given that selenium (Se) is similar in properties to sulfur (S), and that francium (Fr) is similar to sodium (Na), write the formulas for the following compounds. 

Because of the difficulties in obtaining any significant quantities of francium, use of ihe element is confined to scientific investigations. " Fr is used for the measurement ofAc. Studies have shown that francium fixes itself jn induced sarcomas in rats. Because of the short half-lives of - Fr and 2l Fr. which would cause mi radiation risk to organisms, the property could become useful for the early diagnosis of certain kinds of cancers. 

Francium Francium, the heaviest of the group 1A elements, is highly radioactive, and no visible amount of the element has ever been prepared. Little is known about its properties from direct observation, but its behavior would presumably be similar to that of the other alkali metals. 

Look at the properties of the alkali metals summarized in Table 6.4, and predict reasonable values for the melting point, boiling point, density, and atomic radius of francium. 

Using the information on pp. 138-140, predict the properties of the element francium related to its melting point, density and softness. Predict how francium would react with water and write a balanced equation for the reaction. 

Metallic and nonmetallic properties are related to the number of valence electrons and the radius of an atom. Within a period, as the metallic properties decrease from left to right, the nonmetallic properties increase. Within a group as the metallic properties increase, the nonmetallic properties decrease from top to bottom. If the above trends are considered, francium, Fr, would be expected to have most metallic properties. However, since Fr is a radioactive element, not all of its properties have been determined yet. 

The alkali metals — lithium, sodium, potassium, rubidium, cesium, and francium — are members of Group 1 of the Periodic Table, and each has a single ns1 valence electron outside a rare gas core in its ground state. Some important properties of alkali metals are given in Table 12.1.1. 

Actually very, little is yet known about the sixth of these elements, francium, which has been only recently discovered but there is little doubt that francium is closely similar to the other alkali metals in its properties. 

The element phosphorus was named by its discoverer for the property that it glows when exposed to air. Phosphorous in Greek means I bear light. From the names of the elements such as francium (Fr), americium, europium (Eu), berkelium (Bk), and californium (Cf), it is clear that geographic locations were used to name them. Still other elements have been named to honor... 

Until very recendy, there was not enough francium to permit a study of its properties. In 1991, scientists at the State University of New York at Stony Brook developed a method for making small amounts of francium and holding them... 

Predicting of the first 101 elements, francium is the least stable. Its most stable isotope has a half-life of just 22 minutes Use your knowledge about the properties of other alkali metals to predict some of francium s properties. 

In the spirit of Dimitri Mendeleev s prediction of the properties of several, as of then, undiscovered elements, use the given information about the known properties of the alkali metals to devise a method for determining the corresponding property of francium. 

Using the periodic law as a guide, devise an approach that clearly displays the trends for each of the properties given in the table and allows you to extrapolate a value for francium. 

The alkali metals are not found free in nature, because they are so easily oxidized. They are most economically produced by electrolysis of their molten salts. Sodium (2.6% abundance by mass) and potassium (2.4% abundance) are very common in the earth s crust. The other lA metals are quite rare. Francium consists only of short-lived radioactive isotopes formed by alpha-particle emission from actinium (Section 26-4). Both potassium and cesium also have natural radioisotopes. Potassium-40 is important in the potassium-argon radioactive decay method of dating ancient objects (Section 26-12). The properties of the alkali metals vary regularly as the group is descended (Table 23-1). 

The alkali earth metals form Group 1 of the periodic table, made up of lithium, sodium, potassium, rubidium, cesium, and francium (not shown in Fig. 1.3). Their name derives from the observation that their addition to water generates an alkaline solution. They are all low density, soft, and extremely reactive metals, which are rarely found in their metallic form. This group has properties which are closer and more alike than any other group of the periodic table. Since they desperately want to lose their solitary outer sphere electron, their reactions with almost any other species (including molecular oxygen) are violent and explosive. 

Based on your knowledge of the chemistry of the alkali metals, predict some of the chemical properties of francium, the last member of the group. 

Predict the chemical properties of francium, the last member of Group lA. 

Because of their metallic and alkaline properties, potassium and especially sodium are widely used in a variety of industrial processes both as metals and as compounds with various other elements. Lithium is rarely used, but does find application in lightweight alloys with magnesium. Rubidium and cesium are not commonly utilized industrially, except for some applications in electronics. Sodium and potassium are essential for life, sodium being the principal extracellular and potassium the major intracellular monovalent cations. The other alkali metals have no essential biological role, see ALSO Bunsen, Robert Cesium Davy, Humphry Francium Lithium Mendeleev, Dimitri Potassium Rubidium Sodium. 

Because of their metallic properties and low mass, Be and Mg are used to form lightweight alloys for structural purposes. Ca sees less industrial use, although the phosphate is sometimes utifized in fertilizers. Sr and Ba have no significant industrial applications. Both Be and Ra are used in various devices, the former because it is quite transparent to x-rays and the latter because it is a ready source of both a- and y-radiation. Mg and Ca are essential to all living systems for many reasons the other alkali earths have no known biological roles, see also Beryllium Cesium Curie, Marie Sklodowska Davy, Humphry Francium Magnesium Potassium Rubidium Wohler, Friedrich. 

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