Traces of history in the Periodic Table

How we went from four to 110 elements

By Jim Bishop, BEAK International Inc.

There are about 110 elements known to exist. In the 1960s there were about one hundred. A hundred years before that, perhaps 60 were known. This is a far cry from the original four "elements" of fire, water, air, and earth proposed by ancient alchemists in China, Egypt, and Greece. (Although a Greek named Democritus believed that everything was made up out of tiny particles he called "atoms".) The huge expansion in our knowledge came about through the efforts of alchemists to transmutate ordinary metals into gold, and through two of humankind's characteristics ­ our love of beauty, and our fascination with, and inventiveness in warfare.

By 3000 B.C., many metals were well-known in the Middle East. Silver, copper and gold were found as "free" metals in the form of nuggets. They could be worked into a variety of beautiful shapes and ­ especially gold ­ became highly prized for their ornamentation value. Alloys of tin and copper (bronze) could be shaped into tools and weapons superior to those made from stone. Iron, possibly from meteorites that were found and investigated, was fashioned into swords and spears that were vastly superior to the best bronze blades. The arms race was on, as was the race to discover new elements for better weapons and for beautiful jewellery.

Today, we are familiar with many of the elements. We wear gold, silver and sometimes platinum on our fingers, necks, and ears (and some of us in our eyebrows, noses, nipples and navels). We drive machines made out of iron alloyed with other metals, and these machines have shiny parts from nickel, chromium, and zinc. We use batteries made from lead, from lithium and from nickel and cadmium, and we tell the temperature with glass tubes containing mercury. Our dwellings often have siding made out of aluminum, lighting based on tungsten, and pipes made of copper carry water to which we have added fluorine and chlorine. In our kitchens we use sodium chloride (to which we add iodine); if we smoke we light up with matches made from sulphur and phosphorous; if our stomachs become upset we take bismuth compounds, and if we are still not well we may have X-rays after we take a barium cocktail.

Those of us in the environmental business are also familiar with elements that some view as enviro-villains, such as arsenic, mercury, cadmium, uranium, and chlorine. This still leaves us with 70 or 80 elements about which we know or care little.

Many of these other elements do not need to be cared about particularly, as they are only known to exist for fractions of a second in laboratories, or because they are in such short supply that we will hardly be able to find them, let alone use them or otherwise come into contact with them. Examples of the former group are the man-made, laboratory "hot-house" elements that occur on the Periodic Table after uranium, that is, numbers 93 to 110 on the table. These "transuranium" elements became known to us only after the Manhattan Project ­ the effort that led to the development of the atomic bomb in the 1940s. They are unstable, having very short half-lives. A good example is Element 110, of which one atom was manufactured and reported in 1994. It awaits confirmation as do numbers 114, 116, and 118, which were reported this year. Numbers 116 and 118 were created at the Lawrence Berkeley National Laboratory by their 88-inch cyclotron; element 118 decayed in a millisecond; 116 lasted five times as long. Element 114 was announced by Russian researchers; it was viable for a comparative eternity ­ about 30 seconds.

(Note: The Periodic Table accompanying this article shows 103 elements, even though 110-113 are known or thought to exist. It's a case of the printers not keeping up with the physicists.)

Examples of naturally occurring but rare elements are astatine (from the Greek "astatos", meaning "unstable") which has 20 known isotopes, all of which are radioactive, the longest lived of which has a half-life of only 8.3 hours, and francium. Francium, named after France, is an alkali metal like sodium and potassium, but is so rare it is estimated that in our entire planet there are only seventeen atoms of the element at any given time.

So far, we have established that there are 110 elements; we are familiar with about 30 or so, and there are about 20 others that are exceedingly rare or fleeting. We could categorize the elements in this way, but it would be somewhat subjective, and totally redundant, since they have already been categorized and organized in a "Guidebook" to the elements.

This "Guidebook" is the Periodic Table. Mention of the words Periodic Table evokes many emotions, ranging from terror and loathing on the part of the student, to indifference and boredom on the part of non-chemical engineers, and to awe on the part of chemists.

As an environmental chemist, I find the Periodic Table to be the single most useful guide to the world around us. The world, and all of its contents, creatures, and features are made up out of the elements on the table. Not only do we wear and drive the elements, we live in them, we breathe them, and we eat them ­ in short, we are the elements.

Human beings, like other animals, are part of the biosphere, which includes all life on the planet, from the simplest bacteria, to algae and other plants, and all animals including us. The biosphere has been described as the locus of interaction of four of the elements, hydrogen, carbon, nitrogen and oxygen.

These four account for 99% of the mass of the biosphere. However, about twenty other elements are known to be necessary to life, and many others are involved in important reactions at least in some species. If one burns a piece of biomass (as chemists do when they perform an LOI test ­ a test for "Loss On Ignition") the result is that hydrogen, carbon and nitrogen are converted to their oxides, and a tiny amount of ash is left behind.

The ash contains calcium, potassium, silicon, magnesium, sulphur, and many other elements. We know that some are essential to life, but the biochemical functions of most elements are not presently known. Science is only slowly adding to the list of essential elements, mainly because it is nearly impossible to create a "pure" water, food, and air supply for test plants or animals. The word "pure" means a supply that does not contain any of the element being tested. Because an animal or plant's requirement for a trace element may be so minute as to be undetectable, it is simply impossible to construct a control group to determine the effects of withholding the element of interest.

Most of the "essential" elements are relatively "light" ­ that is, they are in the first third of the Periodic Table. Many of the heavier elements, like mercury or lead (numbers 80 and 82) are harmful to the biosphere, and bismuth, number 83, is the last outpost of stability on the table. Beyond it, all the elements are radioactive - they are so overweight they lighten themselves by breaking apart like Michael Palin in a Monty Python skit ­ often with disastrous results for living creatures.

How did we progress from four "elements" to the 110 now known? Not surprisingly, the discovery of many of them is lost in antiquity. The ancient genius who first isolated copper, thereby enabling it to become the first metal to come into widespread use, is not known. What is known is that once the technology for releasing copper from its ores was developed, its use in weaponry and ornamentation became so widespread that all ancient civilizations depended on it. Many ancient powers quickly depleted their own copper resources, and some, like Egypt, developed intricate trading networks to import copper from as far away as the British Isles.

We do not know who first fashioned jewellery from gold or silver, and we do not know who identified and isolated iron, opening the way for the Iron Age that swept the Bronze Age before it. However, we do have reasonable records of discovery since the late 1700s, when oxygen was isolated by Karl Scheele in Sweden and in England by Joseph Priestley.

The discovery of these and other elements will be explored in subsequent articles.

Jim Bishop is President and COO of BEAK International Inc., Brampton, ON. He is a long time member of ES&E's Editorial Advisory Board.