Beryllium and the Alkaline-Earth Metals

Although magnesium and the alkaline-earth metals situated below it in the periodic table form ionic chlorides, beryllium chloride (BeCl2) is a covalent compound. 

Group IIB and know that this means the group of elements zine. cadmium and mercury, whilst Group IIA refers to the alkaline earth metals beryllium, magnesium, calcium, barium and strontium. 

As a consequence of its closed-shell electron configuration, zinc has a negative electron affinity, that is, the removal of an electron from Zn is exothermic. The electronegativity of zinc (1.588 PU) is intermediate between those of the alkaline earth metals and the first row transition metals and remarkably similar to that of beryllium (1.57 PU). 

Some physical and chemical properties of the alkaline earth metals are shown in Table II. It can be seen that beryllium is significantly different from the elements below it in the periodic table in most respects. The fact that the density of beryllium is greater than that of magnesium is perhaps surprising, but can be understood by noting that magnesium is both a more massive and a larger atom. The density of beryllium is to be compared to that of iron (7.9 g cm-3), titanium (4.5 g cm-3), and aluminum (2.7 g cm-3). 

The alkaline earth metal cations follow similar trends to the alkali metal cations in their complexation reactions with monodentate ligands. Hard , class V donor atoms are preferred, and beryllium and magnesium show a greater tendency to form complexes than do their larger congeners. 

Beryllium reacts with fused alkali halides releasing the alkali metal until an equilibrium is established. It does not react with fused halides of the alkaline-earth metals to release the alkaline-earth metal. Water-insoluble fluoroberyllates, however, are formed in a fused-salt system whenever barium or calcium fluoride is present. Beryllium reduces halides of aluminum and heavier elements. Alkaline-earth metals can be used effectively to reduce beryllium from its halides, but the use of alkaline-earths other than magnesium [7439-95 4] is economically unattractive because of the formation of water-insoluble fluoroberyllates. Formation of these fluorides precludes efficient recovery of the unreduced beryllium from the reaction products in subsequent processing operations. 

A remarkable property of the sulphides of the alkaline earth metals and of beryllium and zinc is their power, when certain impurities are present, to exhibit phosphorescence after exposure to bright light. The phenomenon is not due to slow oxidation and is still observable in samples which have been kept hermetically sealed for years it is obvious, therefore, that the effect is a physical one and not analogous to the phosphorescence observable with sulphur (p. 37). The nature and amount of impurity present considerably affect the phosphorescence, chlorides for example causing an increase some impurities inhibit the action.2... 

The Alkaline-Earth Metals.—Magnesium, calcium, strontium, and barium form essentially ionic bonds with the more nonmetallic elements. Beryllium bonds have the following amounts of ionic character Be—F, 79 percent Be—O, 63 percent Be—Cl, 44 percent Be—Br, 35 percent Be—I, 22 percent. 

Solutions of alkali metals in ammonia have been the best studied, but other metals and other solvents give similar results. The alkaline earth metals except- beryllium form similar solutions readily, but upon evaporation a solid ammoniste. M(NHJ)jr, is formed. Lanthanide elements with stable +2 oxidation states (europium, ytterbium) also form solutions. Cathodic reduction of solutions of aluminum iodide, beryllium chloride, and teUraalkybmmonium halides yields blue solutions, presumably containing AP+, 3e Be2, 2e and R4N, e respectively. Other solvents such as various amines, ethers, and hexameihytphosphoramide have been investigated and show some propensity to form this type of solution. Although none does so as readily as ammonia, stabilization of the cation by complexation results in typical blue solutions... 

Volume III. ( Part I. The Alkaline Earth Metals. By May Sybil Burr (nie Leslie), D.Sc. (Leeds). Pp. i-xxvi + 346. 20s. I Part IL Beryllium and its Congeners. By Joshua C. Gregory,... 

Our theory regarding atomic size and reactivity holds true for the alkaline earth metals. As we move down a group on the periodic table, as the atomic size increases, the chemical reactivity increases. Calcium is more reactive than beryllium and magnesium. Neither the alkali metals nor the alkaline earth metals would be good candidates for jewelry making. We would not want to wear metal jewelry that might react violently to oxygen or water vapor in the air. 

Group 1 elements, beginning with lithium (Li) and running vertically to francium (Fr), are called alkali metals. Group 2 elements, beginning with beryllium (Be) and running vertically to radium (Ra), are called the alkaline earth metals. 

---