The name Boron comes from the Arabic and Persian words for Borax that is its principal ore. Although compounds of boron were known in ancient times, it was first isolated in 1808 by Gay-Lussac and Thnard and independently by Sir Humphry Davy (who has a lot of elements to his credit). Boron exists in the earth's crust to the extent of only about 10 ppm (about the same abundance as lead). The pure element is shiny and black. It is very hard and in extremely pure form it is nearly as hard as diamond, but much too brittle for practical use. At high temperatures it is a good conductor but at room temperature and below is an insulator. Its this behavior together with many of its other properties have made it to be classified as a metalloid. In addition to the crystalline form of boron there is also an amorphous dark brown powder. The element can be prepared by the reduction of borax (Na2B4O7) with carbon. High-purity boron can be produced by electrolysis of molten potassium fluoroborate. Borax and boric acid (H3BO3) are among the most common compounds of boron.
Aluminum ranks third on the list of the ten most abundant elements in the earth's crust, while its oxide is fourth among the ten most common compounds in the crust. It is the most abundant metal on the planet. Its name is taken from the Latin Alumen for alum. It is soft, lightweight and silvery and its existence was proposed by Lavoisier in 1787. Later it was named by Davy in 1807 and finally isolated by Orsted in 1825. In its purest form the metal is bluish-white and very ductile. It is an excellent conductor of heat and electricity and finds use in some wiring. When pure it is too soft for construction purposes but addition of small amounts of silicon and iron hardens it significantly. Although it does not seem to be particularly reactive, aluminum is considered an active metal as its behavior is deceptive because it reacts rapidly with the oxygen in the air to form aluminum oxide (Al2O3), or alumina, which is tightly bound to the metal and exists as a dense coating (unlike the oxides of iron). This coating protects it from further reaction. Clearly, however, this coating is not entirely foolproof since aluminum does not exist in native form. Most of the aluminum today is produced by the Hall process which uses significant amounts of energy in the form of electricity to electrolyze aluminum metal from a molten salt mixture. The large initial outlay of energy is one important reason why recycling aluminum is such a good and cost-effective idea.
Gallium is one of the elements originally predicted by Mendeleev in 1871 when he published the first form of the periodic table. He dubbed it ekaaluminum, indicating that it should have chemical properties similar to aluminum. The actual metal was isolated and named (from the Latin Gallia, for France) by Paul-Emile Lecoq de Boisbaudran in 1875. The detective work behind the isolation of gallium depended on the recognition of unexpected lines in the emission spectrum of a zinc mineral, sphalerite. Then eventual extraction and characterization followed. Today, most gallium is still extracted from this zinc mineral. Although once considered fairly obscure, gallium became an important commercial item in the '70s with the advent of gallium arsenide LEDs and laser diodes. At room temperature gallium is as soft as lead and can be cut with a knife. Its melting point is abnormally low and it will begin to melt in the palm of a warm hand. Gallium is one of a small number of metals that expands when freezing.
The element indium (named from the Latin Indicum, for the color indigo) was discovered in 1863 by Reich and Richter. It is a rare metal, with abundance similar to that of silver. It is generally found in deposits with zinc and refineries which produce this more common metal often sell indium as well. The pure metal is so soft that we can "wipe" it onto other materials in much the same way as lead (or even pencil graphite). It is corrosion resistant. As with gallium, identification of indium involved the recognition of new emission spectrum lines (its name was chosen because of indigo lines in its spectrum). Curiously enough, Reich who did the initial chemical isolation work was color blind and had to turn over his experiment to an assistant (Richter) who was the first to observe the characteristic lines. Like pure tin, pure indium emits a squealing sound when bent.
Sir William Crookes discovered thallium in 1861, positively identifying it by a bright green line in its spectrum (hence the name, which is from the Greek, Thallos, for "green twig"). Although in appearance thallium resembles lead, it does not have the corrosion resistance of lead and so has few commercial applications. Thallium compounds are quite toxic and some have been used as rat poisons. A few compounds are used in glasses for special infra-red lenses. In studies announced jointly by the Joint Institute for Nuclear Research in Dubna, Russia, and the Lawrence Livermore National Laboratory in the U.S., four atoms of element 113 were produced in 2004 via decay of element 115 after the fusion of Ca-48 and Am-243.