Francium, Element

A complete review of the theoretical calculations for the electron affinities of atoms is beyond the scope of this book. The quantum mechanically calculated electron affinities of the first and second row elements—the alkali metals, Ca, Ba, and Sr—support experimental results within their mutual uncertainties. 5 meV has been determined to be the best precision and accuracy of theoretical methods for atoms [13]. For example, the calculated values for Li, Na, K, Rb, and Cs agree with the experimental values to within 5 meV. Thus, the AEa of Fr is 0.491(5) eV calculated theoretically. By the same method, the predicted value for eka-francium (element 119) is 0.663(5) eV [41]. The predicted Ea for Ra is also larger than the experimental value for Ba, 0.145 eV. 

Landau, A., Eliav, E., Ishikava, Y., Kaldor, U. Benchmark calculations of electron affinities of the alkali atoms sodium to eka-francium (element 119). J. Chem. Phys. 115, 2389-2392 (2001)... 

The table contains vertical groups of elements each member of a group having the same number of electrons in the outermost quantum level. For example, the element immediately before each noble gas, with seven electrons in the outermost quantum level, is always a halogen. The element immediately following a noble gas, with one electron in a new quantum level, is an alkali metal (lithium, sodium, potassium, rubidium, caesium, francium). 

Relatively little is known about the chemistry of the radioactive Group I element francium. Ignoring its radioactivity, what might be predicted about the element and its compounds from its position in the periodic table ... 

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. 

Francium was first identified in 1939 by the elegant radiochemical work of Marguerite Perey who named the element in honour of her native country. It occurs in minute traces in nature as a result of the rare (1.38%) branching decay of Ac in the series ... 

The six elements adjacent to and following the six inert gases are lithium, sodium, potassium, rubidium, cesium, and francium. These elements have similar chemistries and are called the... 

C08-0045. Determine the atomic number and valence orbital that is filling for the element that would appear below francium in the periodic table. 

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 ... 

Unter den Francium-Isotopen ist das Fr 219 betastabil, d.h. es zerfallt weder durch / +- bzw. K-, noch durch /9"-Emission. Waren ubrigens die Elemente oberhalb Wismut (und somit auch das Fr 219 ) nicht a-Strah-ler, so wiirde das Francium als Fr 219 in der Erdrinde vorkommen (50). 

Da das Francium ein betastabiles Isotop aufweist, ist es kein Lilcken-element. 

All of these elements have only one electron in their outer energy shells.. Even francium, with 87 electrons, has only one in the outer shell. The other 86 are in inner shells. It is easy for the alkali metals to lose that one electron, as hydrogen does, and become positively charged ions. 

If the seventh period of the periodic table is 32 members long, it will be the same length as the sixth period. Elements in the same family will have atomic numbers 32 units higher. The noble gas following radon will have atomic number = 86 + 32 = 118. The alkali metal following francium will have atomic number = 87+32 = 119. 

Francium occurs as a result of the disintegration of actinium. Francium is found in uranium minerals, and can be made artificially by bombarding thorium with protons. It is the most unstable of the first 101 elements. 

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