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Beryllium crystallizes in the hexagonal close packed structure. It is definitely a metal, but a hard and brittle one. Its electron configuration is 1s22s2, so its compounds can be expected to be electron-poor and somewhat exotic. It is a rather small ion, of radius 0.31Å. Its ionic valence is clearly 2, and this is shown in numerous compounds. The first ionizing potential is 9.28V, greater even than that of magnesium. In the halides, the electron transfer is not by any means complete, and these compounds do not ionize easily. The compounds of beryllium are colorless. Aside from these properties, beryllium behaves similarly to aluminium. It is not much like magnesium, calcium or barium, the other elements called the alkaline earths, except in valence. In fact, it is not very alkaline at all, and its oxide and hydroxide are not even soluble. It is not mentioned in qualtitative analysis texts, since it is encountered very rarely. It probably is separated with the aluminium and must then be distinguished from it by the precipitation of a basic carbonate by adding ammonium carbonate. An excess of reagent dissolves the precipitate. Like aluminum, it forms a protective oxide layer on exposure to air, which makes the surface very hard. Beryllium resists atmospheric corrosion at high temperatures better than titanium or zirconium. Above 600°C, the oxide is first formed, and then the nitride, Be3N2 at 1000°C. Metallic beryllium should not be used at temperatures over 600°C.
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