Cinderella Elements

If a person were stopped at random and asked to name as many of the chemical elements as possible, he would readily list about a dozen. With a little prompting, it is likely that this figure could be doubled. If a few names were suggested, the same person would probably admit familiarity with some of them. The full total, however, would be unlikely to rise above about forty. This is fewer than half the existing elements.

Some elements, like oxygen, nitrogen and carbon are everywhere. Most people could mention two or three uses for iron, copper, aluminium and several other elements. They could almost certainly state one use for less familiar elements such as tungsten, perhaps, or vanadium. Even rare elements, such as gold, silver and platinum are well known. But the majority would lie outside their knowledge. The chemistry specialist also, who may well be able to name all the elements, would be hard pressed to give one useful piece of information about a high proportion of them.

Yet many of the lesser-known elements turn up in unexpected places. They often have everyday uses that remain unacknowledged. Some have a variety of functions, while others are limited in their applications. Still others are finding increasing usefulness as technology advances and the demand for new materials with novel properties expands.

Most elements are metals, and as such are often alloyed with other metals to enhance their properties or the range of their applications. Many are not rare, and their lack of use frequently reflects the lateness of their discovery.

Zirconium is more abundant in the earth’s rocks than copper, lead, zinc, tin and other well-known metals. It has been known in semi-precious stones, such as zircon, for many centuries, but was not isolated as the pure metal until 1824. It is non-toxic, environmentally safe and does not corrode at high temperatures. Zirconium metal is used widely to make the cans that hold fuel rods in nuclear reactors, as it does not absorb neutrons and so, unlike other metals, does not become radioactive. Its compounds are replacing those of lead in paints, and its hydrochloride is taking over from the aluminium equivalent in some deodorants. Zirconium phosphate is used in kidney dialysis machines.

The dioxide of zirconium is remarkably strong and stable. It can withstand the corrosiveness of hot acids, alkalis and metals. It is almost as hard as diamond, yet remains as flexible as steel, and is at the forefront of a new generation of ceramic materials.

In the Periodic Table, zirconium is bracketed on the left and right by the metals yttrium and niobium. At temperatures close to absolute zero, minus 273 degrees centigrade, metals will conduct electricity without resistance, a phenomenon known as superconductivity. Alloys containing yttrium and niobium have shown the ability to superconduct at much higher temperatures, a property that has implications for the generation of electricity at low cost.

A compound containing lithium and niobium has shown promise in the field of holography, in which data can be stored and retrieved in 3-dimensional form by the use of lasers.

The elements that appear below yttrium, zirconium and niobium in the Periodic Table also have uses, despite their relative obscurity. Lanthanum, for example, is a metal that gives strength to alloys of aluminium and magnesium and some steels. It is also used to create a spark in lighter flints. Hafnium and tantalum are added to tungsten, the metal with the highest melting point, in the manufacture of the filaments in electric light bulbs.

Near neighbours of these elements, osmium and iridium form alloys that are hard wearing and do not easily corrode. They are used widely in spark plugs and to make the writing tips of pen nibs.

Pollution is a major problem in the modern world. The burning of diesel oil in buses, lorries and an increasing number of cars produces fumes containing particles of carbon that are much larger and more abundant than are found in the exhaust emissions from petrol engines. These particulates can cause lung ailments and may even conceal cancer-causing agents. Small quantities of an oxide of lanthanum’s next-door neighbour, cerium, when added to diesel fuel, effectively eliminates the particulates. As the effect of the cerium oxide is catalytic, it has been estimated that less than 2kg would be sufficient to eliminate this form of pollution for the lifetime of an average diesel engine.

Cerium sulphide is a non-poisonous, red solid, and has become an important alternative to more toxic pigments, such as those containing lead and cadmium, in the manufacture of paints.

Europium, like hafnium, is an element that was not discovered until the beginning of the 20th Century, and has found a uniquely 20th Century everyday use. The colours on the screens of colour televisions are caused by chemicals that phosphoresce when struck by an electron beam. The colours of the earliest TV’s were quite insipid, because of the lack of a red phosphor of sufficient intensity. This problem was solved by the discovery of a europium-yttrium oxysulphide that emits a much stronger red colour than previously used compounds.

Europium was, of course, named after Europe. The American equivalent, americium, which appears directly below europium in the Periodic Table, did not even exist until mid-way through the 20thCentury. It is manufactured in nuclear reactors and is itself radioactive. Despite its obvious dangers, it saves many lives through its employment in smoke detectors and fire alarms. Inside the smoke detector, the radiation from the few micrograms of americium present causes the air to ionise into electrically charged particles. These in turn cause a small electric current to flow in the detector. The presence of smoke interrupts this process and the current falls, triggering the alarm.

The small sample of elements discussed here is by no means exhaustive. As the 21st Century gets under way, new technologies as yet undreamt of will emerge. Some elements exist in such small quantities that they will never find extensive use. Many others, however, have properties that are at present of only curiosity value, but which will undoubtedly provide their own unique solutions to the problems these technologies will pose.

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