Some people regard astronomy or physics or mathematics as the mother of all sciences, but I think it's chemistry, because it tells us how all matter is composed and how the changes that occur with it proceed. Chemistry embraces all other sciences and all the phenomena that we see in them, whether it be physics, astronomy, biology, psychology, sociology or whatever, have chemical foundations. I have been interested in chemistry since I was 10 years old, and since then, all the play of symbols, the wonder of building molecules and formulas from a limited set of fundamental units, getting to know the periodic system and seeing substances with a clearly defined colour, smell and other properties change to something completely different, have always fascinated me.

The tendency of a molecule to exchange a couple of atoms and then suddenly not be itself anymore, but a completely different substance is a curious thing with particular relevance to the origin of life. Most of the atoms are still the same, the molecule may be only slightly different, but somehow it has changed teams, like when a soccer player gets a new contract and changes from an Arsenal player to a Liverpool player. The identity of molecules and football players is a fleeting thing. More on this in the story of carbon.

By clicking on one of the elements in the periodic system below, you will find an article with a lot of interesting information about the element. These articles have been posted on a BBS once, and are therefore a bit primitive graphically. To preserve the original atmosphere around them, I have decided to lay them out in white on black, and use a font with fixed character length to make the molecule models readable. As I update the files and add the missing ones, I'll probably introduce CML and a more modern graphical presentation, probably with more illustrations.

Each file is organised in sections displaying the various aspects of the actual element. The basic physical ones first, then a historic section, a geological section, the chemical section with sub-sections covering analysis and demonstrations, followed by sections of biology and human utilisation. I have particularly designed them to be useful forn chemistry students and teachers of chemistry at all levels. You will find all the basic facts and many of the interesting and curious ones, as well as a good selection of more advanced material. I hope this information will be of use to someone and I appreciate any comments and corrections for my articles.
 
 

I prefer setting it up like this because I do not know any good reasons why the lanthanides should be represented in the main table with lutetium and the actinides by lawrencium. In my opinion, there are too many unnecessary nomenclature changes in chemistry. The IUPAC guys keep on getting together every now and then to cook up new changes for us, like it was their job to give us this year's changes. In my opinion, changes are ok, if there is a reason for them. The recent series of arbitrary changes only add to the textbook budgets of the student and make literature studies more confusing. That is my humble opinion.

SOME MILESTONES IN THE HISTORY OF CHEMISTRY

Human beings have been working with chemicals ever since they took up the first tools in their hands. The ancient Egyptians, Sumerians and Chinese 5-6000 years ago knew a lot about various useful substances, how to mix and transform them and use them for different purposes. It took considerably more time to find the theoretical background for all these transformations. But the Greek philosophers were typical theorists, and in the 6th century BCE, they laid down the first foundations of theoretical chemistry. Their first attempts, however, were rather groping in the dark and far from comparable to the advanced practical chemistry at the time. They wanted to find some kind of primeval matter, which was supposed to have given rise to all other things. Some guessed that all things had come from water, others that fire was the birthplace of all things, some thought that everything had grown up of the earth, and so on. If they had speculated on this thread a little further, they might have arrived at quarks and superstrings, who knows? But eventually, they saw that they couldn't agree on a particular primeval substance, and as a compromise, they decided that there were four: earth, water, air and fire. Thus, they had one representative of each of the three different states of matter: solid, liquid and gaseous, while the fire represents the different forms of energy.

This system of four primeval substances or elements later developed into a curious and quaint complex of ideas: alchemy. But before this, another system arose, founded in the 5th century BCE by Leukippos and his pupil Demokritos from Abdera in Thrace, a rustic place somewhat outside the usual sophisticated Greek cultural sphere. They assumed that if matter could be divided ad infinitum, the pieces of matter would eventually have to become infinitely small, i.e. amounting to nothing, but then matter in reality could not exist. As a consequence, they thought that there had to be one smallest indivisible part of all substances which they called atom, because it was so indivisible. They had numerous followers who called themselves atomists, and some of them thought that not only matter consisted of atoms, but also such things as light, music, thoughts and movement - some kind of extreme quantum theory. It was the opinion of the atomists that the properties of the substances depended only on the shape of the atoms they were made up of, and they weren't that far from the truth if you see their atoms as molecules. The atomic theory was forgotten when the classical civilizations fell in decay. But in the 17th and 18th centuries, when Boyle, Newton and Dalton were looking for a new understanding of the nature of matter, they made good use of the atomist writings.

Meanwhile, Platon had founded the world's first Academy in Athens, and his greatest pupil, Aristoteles, probably the first professional scientist in history, performed a magnum opus in collecting and collating the knowledge of his day which made him enormously famous and respected. And when he rejected the atomic theory, it was doomed, at least for a couple of millennia. But he was the father of modern science. Roughly, we use the same division of the various sciences as he did. And he created a scientific methodology which has been the basis for all later scientific work.

Aristoteles embraced the theory of the four elements, and thus, it became the basis for all thoughts about matter transition and the composition of matter in the following centuries. Hence, theoretical chemistry was sent on an erratic side-path, groping in the medieval darkness, and practical chemistry continued developing apart from it in response to the everyday needs of the people. Thus chemistry became the people's servant, without a life of its own, which was admirable enough, perhaps, but any deeper understanding of the nature of matter and matter transitions did not ensue.

Still, there were a few people doing theoretical chemistry work. Originating in classical Alexandria, with the extensive practical chemical knowledge of the Egyptians as a basis and with impulses from the whole Hellenistic world, a class of laborators grew up swarming around the Aristotelic element theories. The alchemists. They continued spreading throughout the new Roman and Arabic empires, with support from a group of alchemists growing up independantly in China. Alchemy is an Arabic word originating from the Greek khemeia, meaning to pour something out or into something, a common activity for alchemists. They developed some laboratory equipment, particularly connected with distillation, and discovered some new substances, which sometimes found practical use so they could sell them for their lives' sustenance. But their main efforts were directed towards a goal they never reached. Goldmaking.

In antiquity, 7 metals and 7 celestial bodies were known, and the alchemists connected them with each other and gave them common symbols. Mercury was quicksilver (or mercury if you prefer), Saturn was zinc, Mars iron, Jupiter tin, Venus copper, the Moon silver and the Sun gold. Each of the celestial bodies ruled its own metal, and they thought the metals germinated and grew down below under the celestial influence and grew more noble the longer they remained down there. They hoped to recreate this process in the laboratory. It's hard to understand what made them keep on like this for centuries, but probably it was sometimes rumoured that someone had succeeded, but kept the secret to himself, spurring things on. The goal, which implied limitless wealth, also must have been empting.

The elements known as distinct substances from antiquity were carbon, sulfur, iron, copper, zinc, silver, tin, gold, mercury and lead, but they were not thought of as elements, there were no reasons known why these could not be transmuted like other substances. Among all the substances discovered by alchemists as far as the 17th century, with some help from miners, there were also some elements: phosphorus, arsenic, antimony, platinum and bismuth. Some of them were recognized as metals, and they posed a problem for the outlook of the world, for what planets were their masters? When Galileo Galilei discovered the moons of Jupiter in the early 17th century, there was some relief, and around 1800, when alchemy was dying, the alchemists clung to Uranus and all the new asteroids that were being discovered as a defense.

When the medieval age was finally over, some alchymists started thinking more independantly, and one of them, Theophrastus Bombastus von Hohenheim (who had the good sense to take the name Paracelsus) split up with them in the early 1500s and founded a new branch of science called iatrochemistry, with the main purpose of producing drugs and find out about the processes of life. This branch became a refuge for the more serious workers in chemistry for the next couple of centuries. In 1662, the Irish naturalist Robert Boyle published "The Sceptical Chemist", where he forswore gold making and redefined the word "element" in the same sense of purity and intransmutability that we use today. He also mentioned the fundamental difference between mechanical mixture and chemical compound. In 1789, Antoine Laurent Lavoisier revolutionised chemistry when he published "Traité élémentaire de chimie", giving a clear, modern definition of an element and presenting the first list of elements, and he introduced chemical equations and a nomenclature for naming inorganic substances. Another, less consequential revolution sadly took his life in 1793. John Dalton founded modern atomic theory in his work "System of Chemical Philosophy" from 1807. He found that the elements combined with each other in simple numerical relations and presented the first list of atomic weights.

Lavoisier's list of elements contained all substances which were not found to be compounded until then. Some were really elements: oxygen, nitrogen, hydrogen, sulfur, phosphorus, charcoal(carbon), antimony, arsenic, bismuth, cobalt, copper, gold, iron, lead, manganese, quicksilver, molybdenum, nickel, platinum, silver, tin, tungsten and zinc, 23 in all. Others were the "radicals" of acids which were thought to contain an element: hydrochloric acid(chlorine), hydrofluoric acid(fluorine) and boric acid(boron). The rest were "earths" or oxides which one could prepare salts from, and which were thought to be elements: lime or calcium oxide, magnesia or magnesium oxide, barytes or barium oxide (also used as a name for other barium compounds), earth of clay or aluminium oxide, and silica or silicium oxide. Thus, in total, he recognised 31 elements. In addition, his list included light and heat (or caloric, as he named it), which are not reckoned among the elements today. Compounds of the two alkali metals sodium and potassium had been known since antiquity, but since they were similar to the ammonium compounds, Lavoisier thought they were compounds like the ammonium ion, which had already been resolved into hydrogen and nitrogen.

With Lavoisier's list and definition in their hands, the chemists intensified their search for new elements. Already the same year, the German chemist Klaproth found two new elements in minerals, zirconium, being the "essence" of the mineral zircon, and uranium, which he named for a planet in the alchemic fashion, the newly discovered Uranus. Klaproth repeated this in 1803, when he named the element cerium for the recently discovered minor planet Ceres, and another minor planet, Pallas, inspired the English chemist Wollaston to name his new element palladium the same year. In the meantime, a series of "earths" extracted from minerals were investigated and found to contain unknown elements: tellurium (named for the Earth herself, or Tellus in Latin - this was also Klaproth's doing), titanium, yttrium, beryllium, chromium, vanadium, niobium, tantalum, rhodium and osmium, things were happening really fast around the turn of that century. The Cornish chemist Humphry Davy invented electrolysis, and from 1807, this lead to the discovery of a series of alkalies and halogens: potassium, sodium, magnesium, calcium, strontium, barium, iodine, lithium and bromine, while boron, aluminium and silicon were isolated for the first time and new analysis of old and new minerals lead to the discovery of cadmium, selenum, ruthenium and thorium.

Then the Swedish chemist Carl-Gustaf Mosander discovered lanthanum in 1839, in a mineral which also contained yttrium. Soon, it was found that the yttrium also was impure. This lead to the apparently endless task of separating and isolating the rare earth elements, which were nearly identical in their chemical properties. Mosander's lanthanum also turned out to have impurities. Erbium, terbium, ytterbium, samarium, holmium, scandium, thulium, neodymium, praseodymium, gadolinium, dysprosium, europium and lutetium were added between 1843 and 1907 after endless series of fractioned crystallizations. By 1860, Wilhelm Bunsen and Gustav Robert Kirchhoff, one of the first of a highly fruitful series of "marriages" between chemistry and physics developed light spectroscopy to a sensitive tool and they and others revealed cesium, rubidium, thallium, indium and helium due to their unique spectral lines.

The simple medieval system of four elements was gone. Lavoisier's list already was confusing enough, but now, it had grown more than twice as long. Who could clear up the mess? Johann Wolfgang Döbereiner noticed that some of the new elements were similar to one another. In 1829, he set up some of the chemically similar elements in triads, where the atomic weight and the physical properties of the middle element was roughly an average of the two others: e.g. lithium-sodium-potassium, calcium-strontium-barium, nitrogen-phosphorus-arsenic, sulfur-selenium-tellurium and chlorine-bromine-iodine. Still, the chemical elements seemed not so easily organized in groups of three, the chemists soon agreed that magnesium belonged to the calcium group, antimony and bismuth to the nitrogen group, oxygen to the sulfur group and fluorine to the chlorine group. Some of the most characteristic groups acquired their own names, halogens, alkalies (alkali metals), alkaline earths, rare earths a.s.o.

In 1862, Alexandre-Émile Beguyer de Chancourtois plotted the elements on a cylinder according to their atomic weights and found that the varations in properties were periodic with 16 atomary weight units between the lightest elements. He called it the tellurian spiral. In 1864, J.A.R. Newlands arranged the 7 first elements in a row like the tunes in a chromatic scale, and continued with rows of 7 below the first one. This resulted in vertical rows of similar elements, and he formulated this in a "law of octaves", as he called it. Unfortunately, this worked only as far as calcium, and his work was rejected by the magazine he had sent it to. In 1869, Dimitri Ivanovich Mendeleyev noticed that the valences of the elements rose and sank in periods. He organised them in a table where he grouped them vertically according to their main valence: 1(H,Li,Na,K,Cu,Rb,Ag,Cs,Au), 2(Be,Mg,Ca,Zn,Sr,Cd,Ba,Hg), 3(B,Al,Y,In,La,Tb,Er,Tl), 4(C,Si,Ti,Zr,Sn,Pb), 5 or -3(N,P,V,As,Nb,Sb,Ta,Bi), 6 or -2(O,S,Cr,Se,Mo,Te,W), 7 or -1(F,Cl,Mn,Br,I) and 8(Fe,Co,Ni,Ru,Rh,Pd,Os,Pt). Thus, he solved Newlands' problem in that he allowed the later periods to be longer than the early ones. The system was neat and clean, but many were sceptical, particularly because he had to place tellurium before iodine despite its higher atomic weight. Also group 8 didn't adhere particularly well to the system. In addition, he needed to allow some gaps in his system to make it right, and had the audacity to predict that new elements would be found in these gaps and even dared predict their properties following Döbereiner's principle of the triades. The two missing elements in group 3 he named eka-boron and eka-aluminium, and the one in group 4 eka-silicon. Then, gallium was discovered in 1875 and turned out to fit his predictions for eka-aluminium remarkably, and the same thing happened with scandium (eka-boron) in 1879 and germanium (eka-silicon) in 1886. A great success for the periodic system, and now it was accepted worldwide, but a shadow of doubt remained because of all those new lanthanide discoveries. Group 3 was becoming very crowded.

No problem was caused however by the discoveries in William Ramsay's laboratory towards the end of the century, a series of gases which were even more noble than the metals in the platinum group and were placed together with them: argon, neon, krypton and xenon. Helium also turned out to belong there. The discovery of radioactivity in 1896 then lead to a series of new elements whose properties were analysed and their group alignments promptly assigned: radium, polonium, actinium, radon and later protactinium. X-ray experiments demonstrated that the atomic number was more than an arbitrary sequence number, it was identical to the charge of the nucleus. Measurements then proved that elements with a charge of 43, 61, 72, 75, 85 and 87 units were missing. In the 1920s, hafnium (72) and rhenium (75) was found after thoroughly working up minerals of neighbouring elements. More working up followed to find the elements missing in position 43 and 61, but without succes. Since 85 and 87 were missing in the natural radioactive series, they were not expected to be found in nature.

Now, it had been found that the atomic nuclei weren't as indivisible as the name implies after all. In 1919, Ernest Rutherford caused the first artificial nuclear reaction by bombarding nitrogen with alpha particles to make oxygen. Such bombardments were to become high fashion in the ensuing time, and the scope of the nuclear reactions were also extended with various means to accelerate the projectiles. These methods were used to synthetize technetium (43) in 1937, the first artificial element, francium (87) in 1939 and astatine (85) in 1940. By then, experiments had been going on for years to find elements beyond uranium as well, the so-called transuranium elements. But when uranium was irradiated with neutrons to produce heavier nuclei, a lot of light nuclei were formed instead. It turned out that uranium was actually dividing. And the calculations showed that immense amounts of energy were liberated in the process. Thus, the nuclear chemists suddenly became very important people and started playing a role in world politics.

Using particle accelerators, neptunium and plutonium were produced in 1940 and then curium in 1944. Neutron irradiation in reactors gave us americium in 1944 and californium and berkelium in 1949. Promethium (61) was finally unveiled in nuclear waste in 1945. Einsteinium was found in 1952 and fermium in 1953 in the debris after a nuclear test, these were also made by the capture of neutrons. But fermium has an isotope which breaks up when it encounters neutrons, so from now on, element synthesis was the accelerators' work again. The superpowers raced each other for the biggest cyclotrons and the longest linear accelerators, but the new elements were ever more unstable, and produced in smaller and smaller amounts. Mendelevium came in 1955, nobelium in 1958, lawrencium in 1961, rutherfordium in 1964, dubnium in 1967, seaborgium in 1974, bohrium in 1976, meitnerium in 1983 and hassium in 1984. Those that are discovered later still have no names, these are no. 110 which came in 1994, no. 111 which came in 1995, no. 112 in 1996 and 114, 116 and 118, all from 1999, a year which shares the 5th place in number of element discoveries with 1803 (Rh, Pd, Ce) and 1940 (At, Np, Pu). Only 1808 (B, Mg, Ca, Sr, Ba), 1898 (Ne, Kr, Xe, Po, Ra), 1879 (Sc, Sm, Ho, Tm), and 1886 (F, Ge, Gd, Dy) are ahead.

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