Caesium Properties

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. 

The Group 1 elements are soft, low-melting metals which crystallize with bee lattices. All are silvery-white except caesium which is golden yellow "- in fact, caesium is one of only three metallic elements which are intensely coloured, the other two being copper and gold (see also pp. 112, 1177, 1232). Lithium is harder than sodium but softer than lead. Atomic properties are summarized in Table 4.1 and general physical properties are in Table 4.2. Further physical properties of the alkali metals, together with a review of the chemical properties and industrial applications of the metals in the molten state are in ref. 11. 

The collected papers of a symposium at Dallas, April 1956, cover all aspects of the handling, use and hazards of lithium, sodium, potassium, their alloys, oxides and hydrides, in 19 chapters [1], Interaction of all 5 alkali metals with water under various circumstances has been discussed comparatively [2], In a monograph covering properties, preparation, handling and applications of the enhanced reactivity of metals dispersed finely in hydrocarbon diluents, the hazardous nature of potassium dispersions, and especially of rubidium and caesium dispersions is stressed [3], Alkaline-earth metal dispersions are of relatively low hazard. Safety practices for small-scale storage, handling, heating and reactions of lithium potassium and sodium with water are reviewed [4],... 

A remarkable property of the atomic weights was discovered, in the sixties, independently by Lothar Meyer and Mendeleeff. They found that the elements could be arranged in rows in the order of their atomic weights so that similar elements would be found in the same columns. A modernised form of the Periodic Table will be found on pp. 106, 107. It will be noticed, for example, that the "alkali" metals, Lithium, Sodium, Rubidium and Caesium, which... 

The properties of the alkali metals and of their salts are roughly functions of the at. wt. of the metals. There is generally a break in the curve about potassium so that lithium and sodium form one series, and potassium, rubidium, and caesium another. The properties of the series, K, Rb, Cs generally change more regularly than the series Li, Na, K, although some irregularities do occur—e.g. the m.p. of the nitrates. 

Chemical properties.—Sodium chloride is necessary for the proper performance of the physiological functions of the body the other alkali chlorides are said to be poisonous 64 with small animals. According to C. Richet, the maximum dose per kilogram of animal, with subentaneous injections, is 01 grm. with lithium chloride 0 5 grm. with potassium chloride l O grm. with rubidium chloride and 0 5 grm. with caesium chloride. Lithium chloride is very hygroscopic sodium chloride is less hygroscopic, but it takes up O 5 to 0> 6 per cent, moisture on exposure... 

The replacement of potassium by rubidium, or rubidium by csesium, produces a regular increase in the dimensions of the crystal, and the same regularities occur in the optical properties. The same regularities do not occur with sodium and lithium. A. Ogg and F. L. Hopwood have calculated the lengths of the sides and the volume of the unit rhomb of the crystals potassium, rubidium, and caesium sulphates from data furnished by the X-ray spectrometer they find... 

It will be observed that the m.p. of rubidium nitrate is lower than that of potassium nitrate, while that of caesium nitrate is higher. This is an unusual sequence in the properties of the alkali salts—see the solubilities for another irregularity. 

Caesium is a metal in Group I of the Periodic Table, a State two physical properties of caesium. [2]... 

Metallic substances vary in hardness from, e.g., sodium and gallium which can easily be cut with a knife, to very hard materials such as tungsten, which finds applications in making drills etc. Their melting and boiling points are equally variable, and correlate fairly well with their hardness. Thus caesium and gallium melt just above room temperature, while tungsten melts at 3380 °C. The most characteristic properties of metals are ... 

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