This is the sequel post to Wonderful Words of Science I and Wonderful Words of Science II, in which I cover some of my favorite derivations of words from science. In this third and final installment, I’m going to focus exclusively on the names of the elements.
Since my starting point for most of these derivations is Asimov’s Chronology of Science and Discovery, each term is followed by a page number that references Asimov’s book.
Hydrogen (231). You don’t have to be an etymologist to figure out hydrogen’s derivation: hydro- is “water” and -gen is “forming” (as in generating). But the fun of etymology isn’t just knowing where a term came from, but also learning something deeper about the thing named. Hydrogen’s first name was the much cooler fire-air, because, as the unfortunate souls that died in the Hindenberg learned, hydrogen is explosively flammable. In 1784, Henry Cavendish, who had named fire-air, now reported that the combustion of hydrogen in normal air produced pure water. The great chemist Antoine Lavoisier therefore gave fire-air the less cool, but more dignified name of hydrogen. Of course, we now know that two molecules of hydrogen gas (H2) combines readily with Oxygen gas (O2) to yield two molecules of water (H2O). This reaction also releases an explosive amount of energy. In everyday life, we use water to put out fires, but the irony of hydrogen (the water-former) is that it produces the fire and the water at the same time. In fact, liquid hydrogen mixing with liquid oxygen was a major component of the Space Shuttle’s thrust. Our cars may be polluting the atmosphere, but our rocket ships, largely, just made clouds of water.
Helium (353). Helium has one of the most unusual discovery stories of all of the elements, though it owed its discovery to the use of spectroscopy, the same technique that led to the discovery of many elements. Spectroscopy had its origins in 1666, when Isaac Newton showed that light from the sun is composed of many wavelengths of light. In 1814, Joseph von Fraunhofer refined Newton’s observation, demonstrating that certain wavelengths (some 600) were missing from sunlight passed through a narrow slit and then through a prism. In 1859 this was further clarified when Gustav Kirchhoff demonstrated that pure elements, when heated, only gave off particular wavelengths, and these wavelengths were specific to the element in question. It became clear that the “missing wavelengths” of Fraunhofer were evidence of elements in the sun’s atmosphere absorbing the element’s particular wavelengths, which meant one could study the light coming from a star and know what elements existed in that star (once one worked out the characteristic spectral lines of each element). It also meant that if one purified a compound, heated it up, and was unable to match the spectral lines given off to any known element, the sample consisted of an undiscovered element. Kirchhoff went on to discover several elements in this fashion (see below). By 1868, many elements had been discovered, but the second-most common element in the universe – helium – had not, for two very good reasons. One, helium is a noble gas, meaning it does not form compounds very easily with other elements, and so helium pretty much can only exist as isolated atoms. Hydrogen, by contrast, combines easily and exists all over the earth in the form of water and carbohydrates to name two prominent sources. Second, helium is very light – so light that, as a free atom, it escapes effortlessly into outer space. The only helium on earth is the helium created by the radioactive decay of rare elements like uranium, and only stays around if it is formed well underground and trapped by layers of rock. So how was helium discovered? In 1868, Pierre Jansen and Joseph Lockyer studied the sun’s spectrum during an eclipse and found dark spectral lines corresponding to no known element. This unknown solar element was named helium after helios, the Greek word for sun. Eventually, when people started studying uranium ores, the same spectral lines were observed in a gas escaping from those ores, and so helium was confirmed. But helium is an element discovered on the sun 27 years before its discovery on Earth!
Rubidium (336). One of the first elements that Kirchhoff identified with his new technique (along with Robert Bunsen, of Bunsen burner fame), in 1861, was rubidium (Rb, atomic number 37). The name comes from the Latin rubidus, meaning “dark red” – even though rubidium is a chalky-white metal. The redness isn’t the color of the element, but rather one of its tell-tale spectral lines (I assume the one furthest rightward in the emission spectrum below – it’s faint). Rubidium set aflame will also glow reddish, and in a mixture with other compounds, gives the purple color to fireworks.
Cesium (336). Cesium was discovered shortly before rubidium, also by Kirchhoff, and was named in the same manner. In this case, sky-blue emission lines were definitive, so the discoverers named the element from the Latin caesius, meaning “sky-blue”. When I saw that, I wondered immediately if Julius Caesar’s name was also derived in similar fashion, but the jury appears to be out. According to a Wikipedia article, there are 4 theories about Caesar’s name, one of which refers to bluish-grey eye color (caesius) and another of which refers to a story that he killed an elephant (caesai) which is a bluish-gray animal. In any event, the element was named for the color, not the Emperor.
Thallium (341), Indium (345). These elements were also named for the color of their important spectral lines – thallium from thallos (Greek for “green twig”) and indium for the color indigo. Because there are quite a few elements named for places, I had always assumed that indium was named for India. In a way, it is – because the Greek word indikon, which gave us our word indigo, was used in Greek to mean “blue dye from India”.
Cobalt (193). Speaking of the color blue, I had always assumed that cobalt was named for a bluish color. In this case, though, the etymology is the other way around: we speak of “cobalt blue” because cobalt salts have a bluish color. Which is good, because we’ve talked enough about colors, and cobalt has a much more interesting etymology than that. Cobalt is chemically similar to the valuable copper, and so miners were sometimes fooled in expending effort to recover a useless metal (useless at the time, in any event, compared to the copper or silver they were looking for). Either playfully or purposefully, the metal was named for the kobold, a mythological evil spirit in German lore, who was proposed to have stolen the useful metal and replaced it with a worthless one. (The word goblin is apparently related.) For anyone who encountered kobolds and goblins in teenage games of Dungeons & Dragons, there’s no more impressive elemental etymology than that of cobalt.
Nickel (201). It might be nice if German miners had named all of the elements on the Periodic Table, but as far as I know, they only named two – but they made them count. Sometimes they came across a deposit of another non-copper, non-silver ore which didn’t look like cobalt, but which wasn’t doing them any good either. This one they called kupfernickel, which Asimov translates as “Old Nick’s copper” – Old Nick being one of the names people use for the Devil. When an element was isolated from the kupfernickel ore in 1751, the “kupfer/copper” portion of the name was dropped and it became nickel.
Dysprosium (387). The Periodic Table has a fascinating discontinuity of sorts – there are two rows that are customarily separated from the rest of the table and placed on their own down underneath the main body of the table. These rows are called the lanthanide series and the actinide series after their first elements (lanthanum, La, atomic number 57, and actinium, Ac, atomic number 89). In earlier rows (periods) of the Periodic Table, each column (group) of elements exhibits similar chemistry distinct from the neighboring group. For example, sodium and potassium (in the same group) form monovalent cations and will form ionic bonds with chloride (forming NaCl or KCl). One group over, elements such as magnesium and calcium form divalent cations that bond with two chloride ions (forming MgCl2 and CaCl2). However, because of the electron orbital arrangement of larger atoms, the elements in the entire lanthanide series behave very similarly to one another (and the same is true of the actinides). The consequence is that ores containing multiple lanthanides will be very hard to separate into individual elements, which made identifying these elements particularly challenging. Indeed, the name lanthanum comes from the Greek lanthanein, which means “hidden”. Dysprosium, one of the lanthanides, is from the Greek dysprositos, meaning “hard to get at.”
Neodymium, Praseodymium (385). Another example of the difficulty in isolating the lanthanide elements is the story of praseodymium and neodymium, atomic numbers 59 and 60. In 1885, Carl Auer was working with an ore called didymium, which, for 4 decades, had been assumed to be an element. In fact, the name didymium means “twin”, because it seemed so similar to other lanthanides which were known. But twin turned out to be an ironic name – because Auer discovered that didymium was not an element, but was an ore containing two elements that were themselves like twins to one another. One he called praseodymium, meaning “green twin.” Asimov reports that this was for the color of its spectral lines, but another source says the green refers to the color of the oxide of the compound itself. (Both are plausible, as the spectral lines and the praseodymium oxide have ample green.) The heavier “twin” was called the “new twin” (neodymium).
Neon, Krypton, Xenon (411). I mentioned earlier that helium exists on Earth only as the result of radioactive decay and that, because it is light and essentially inert, it escapes Earth’s gravity shortly after formation unless trapped in the bowels of the Earth. The other virtually inert elements, such as neon, argon, krypton, and xenon, are likewise hard to detect, but they are too heavy at least to escape into space. Still, they aren’t easily captured and analyzed, but in 1898, the ability to create ultra-cold temperatures in the lab had advanced considerably, allowing William Ramsay and Morris Travers to study liquified air. Because different components of air would be expected to have different boiling points, the chemists carefully raised the temperature of liquified air to analyze vapors produced at different temperatures, and then used spectroscopy to analyze what they had found. In this way they found something “new” and from the Greek word for new, named the gas neon. Earlier they had found another “hidden” element in the air, and so named it krypton after the Greek word kryptos, “hidden one” (ala cryptic). And a little while later they found another element no one had met before, which became xenon, from xenos “stranger” (which also gave us xenophobia, the fear of foreigners). As for the other noble gases, Ramsay had a hand in finding argon. The approach to finding argon was to remove the known components of air (oxygen, nitrogen, water, and carbon dioxide) and, since compared to argon the other noble gases are just traces, its properties could be studied. Because it was so inert it was given its name – argon means “no work” or, more pejoratively, “lazy”. The final noble gas, radon, is a bit of a special case – it is formed from the radioactive decay of heavier elements, and so was discovered when radioactivity became a hot topic (unintended pun) in the early 1900s. Different radon isotopes are formed from the breakdown of actinium, thorium, and radium, and so, for a short while, there were gases called actinium emanation, thorium emanation, and radium emanation. These became actinon, thoron, and radon by contraction, and, when they were all determined to be isotopes of the same noble gas element, one of the three names (radon) was chosen. Radon itself is unstable (radioactive) and, because it is a gas, is a relatively unique radioactive danger.
Technetium (530), Promethium (554). Speaking of unstable elements, almost all of them are large (with atomic numbers of 84 or more). Because like charges repel, packing multiple protons into a nucleus creates potential instability. However, protons and neutrons are subject to the strong nuclear interaction which holds the nucleus together. The strong interaction, however, decays very quickly with distance, and so, if the nucleus becomes too large, the strong interaction may be insufficient for nuclear stability. Even smaller elements, though, can have unstable isotopes if the balance of protons and neutrons is not ideal. Even little hydrogen has an unstable isotope (tritium, with one proton and two neutrons) as does, for example, carbon (carbon-14, whose radioactive decay provides a means of carbon dating archeological relics made of plant matter). Two elements with atomic number 43 and atomic number 61 apparently have an unfortunate number of protons, from a nuclear stability perspective because, no matter how many neutrons are added to the nucleus, nuclei with 43 or 61 protons can never be stable. For this reason, these two elements haven’t existed on Earth for a very long time, and so they were not discovered until long after neighboring elements, like molybdenum and ruthenium, in the case of atomic number 43, were discovered. The inability to find element 43 was particularly frustrating given that all of the elements of similar size were known, so the physicist Emilio Segre took matters into his own hands in 1937 and bombarded molybdenum with neutrons, hoping to form element 43. (You’d think he’d need to bombard molybdenum with protons, but protons are positively charged and so are repelled by positively charged atomic nuclei. A neutron of the right energy has a much better chance of being “accepted” by the nucleus which rapidly accommodates the extra particle by converting the neutron to a proton and emitting beta radiation.) Segre was successful, and named element 43 technetium from the Greek technetos, “artificial.” Element 61 was discovered among the fission products of uranium at the Oak Ridge National Laboratory and dramatically named promethium after Prometheus, the Greek God who stole fire from Mt. Olympus to give to mankind, a poignant reminder that man was creating elements in ways only previously possible in the heavens (that is, in stars).
Astatine (542). Segre also synthesized atomic number 85 in 1940 in order to fill another vexing gap in the Periodic Table. He did this by hammering bismuth with alpha particles, which are essentially helium-4 nuclei. This required even more energy than neutron bombardment and was only possible with the development of higher-energy cyclotrons. Element 85 was created, but was so unstable it broke down by radioactive decay rapidly (with a half-life of 7 hours). For that reason, Segre’s group named it astatine, from the Greek word astatos (a-, not; –statos, static or stable).
Elements named for places in the Solar System. Helium is not the only element named after an astronomical body, but it is the only one whose name indicates where it was discovered. The others are uranium, neptunium, plutonium, cerium, palladium, tellurium, and selenium. Uranium was isolated from its ore pitchblende in 1789, just a few years after William Herschel’s discovery of the planet Uranus. Since this was the first planet discovered since the time of the ancient astronomers, this was truly a watershed event in science, so it seemed natural for uranium’s discoverer (Martin Klaproth) to honor that. Neptunium and plutonium were synthesized in 1940 and, since they lay just beyond uranium on the Periodic Table, they were named for the planets Neptune and Pluto which lay just beyond Uranus in the Solar System. Cerium was discovered by Klaproth simultaneously with Jakob Berzelius in 1803, and Berzelius suggested the name to honor the discovery of Ceres two years earlier. As the first asteroid discovered (large enough that it is now grouped with Pluto as a dwarf planet), it was another celebrated discovery worthy of the Periodic Table honor. Palladium honors another asteroid, Pallas. Tellurium was named by Klaproth from tellus, the Latin word for Earth, which is ironic since tellurium is more common in stars than on planetary bodies, including Earth. Selenium was named by Berzelius from the Greek word selene (“moon”) because it was chemically similar to tellurium and therefore deserved a name that indicated that kinship. The element mercury, which may seem to be another candidate for this section, was named for the Roman god, not the planet (the planet was, of course, also named for the god). Mercury was the messenger god, renowned for his speed, and mercury the element is also called quicksilver for its ability to avoid being picked up. The etymology of the symbol Hg, incidentally, is from the Greek hydrargyrum (“water-silver”), honoring mercury’s liquidity and silver color. The prefix (hydra) is water and the suffix (argyrum) is silver. This also explains why the symbol for silver is Ag (though this comes more directly from the Latin argentum).
Elements named for colors. A couple of the derivations presented previously come from colors – either the color of prominent spectral lines or the color of compounds containing the element itself. In addition to those listed above, color is responsible for the etymology of chlorine (khloros, Greek, “pale green”), chromium (chroma, Greek, “color”), arsenic (zarnik, Persian, referring to a golden-colored mineral), zirconium (zargon, Persian, “gold-like”), rhodium (rhodon, Greek, “rose”), iodine (iodes, Greek, “violet”), iridium (iris, Latin, “rainbow”), bismuth (wismuth, German, “white mass”), and probably gold (gold, Anglo-Saxon, “bright yellow”), as well. Still other elements were named for other visual aspects, such as molybdenum (molybdos, Greek, “like lead”).
Elements named for other sensory features. The element aluminum (alumen, Latin, “bitter salt”) was named for a bad taste, bromine (bromos, Greek, “stench”) and osmium (osme, Greek, “smell”) for a bad smell, and barium (barys, Greek, “heavy”) and tungsten (Danish, “heavy stone”) for being heavy.
Elements named for people. The latest craze in element-naming is to honor famous scientists, sometimes element-hunters, sometimes others. In fact, most of the synthetic elements (those not naturally-occuring) are named either for people or for the laboratories, cities, or countries in which the elements were synthesized. The eponymous elements are: gadolinium, curium, einsteinium, fermium, mendelevium, nobelium, lawrencium, rutherfordium, seaborgium, bohrium, meitnerium, roentgenium, and copernicium. The honorees, in order, are: Johan Gadolin (discovered yttrium), Pierre and Marie Curie (discoverers of polonium and radium), Albert Einstein (Nobel Prize-winning physicist), Enrico Fermi (Nobel Prize-winning physicist), Dmirtri Mendeleyev (author of the Periodic Table), Alfred Nobel (inventor and founder of the Nobel Prize), Ernest Lawrence (Nobel Prize-winning physicist who designed the cyclotron), Ernest Rutherford (Nobel Prize-winning physicist who discovered the proton), Glenn Seaborg (Nobel Prize-winning chemist for work on the actinide series), Niels Bohr (Nobel Prize-winning physicist for work on electron orbitals), Lise Meitner (who discovered nuclear fission), Wilhelm Roentgen (Nobel Prize-winning physicist for discovery of x-rays), and Nicolas Copernicus (who described the sun-centered solar system). Considering that Einstein famously encouraged the United States to research the atomic bomb, and Enrico Fermi was largely responsible for the first successful nuclear reactor, it is fitting that einsteinium and fermium were discovered in the rubble of a 1952 atomic bomb test. And a footnote about copernicium: the name Copernicus comes from a town, Koperniki, that was probably named after copper that was mined there. So in a sense, the element copernicium was named for a man, Copernicus, who was named for an element, copper.
Elements named for mythological “people”. Besides cobalt, nickel, promethium, and mercury, described above, several other elements get their names from mythology. These are: titanium, vanadium, niobium, cadmium, tantalum, and thorium. Titanium was named for the Greek Titans, although another etymological explanation is that it was named from the Greek word titan, which means Earth (and thus it would belong with the Solar System elements). Tantalum is from Tantalus, the Greek mythological figure who was punished (“tantalized”) by having fruit and water visible but just out of reach; like dysprosium, this was a name that presumably reflected the difficulty in characterizing such an inert element. Indeed, it was confused with another element often found with it which, when isolated, was named niobium after Niobe, daughter of Tantalus. The Greeks also gave us cadmium, from Cadmus, the mythological founder of Thebes (but only indirectly). The other elements on this list come from the Norse myths – thorium, from the thunder god Thor, and vanadium, from Vanadis, the goddess of beauty.
Elements named after locations. There are, by my count, a minimum of 29 elements named after places – continents, countries, regions, cities, rivers, and laboratories. But I think I’d better quit while I’m ahead… or maybe, more accurately, just a little bit behind.