Element Tales: A Meandering Stroll Around 118 Elements

On 7th Feb this year Mark Lorch, a chemist and science communicator at the University of Hull, had the idea to start an element association game. Could a determined bunch of Twitter chemists find a path through all 118 elements of the periodic table in honour of Periodic Table Day and the International Year of the Periodic Table?

It turned out that they could! #ElementTales started with mendelevium, and meandered — avoiding a few forks — all the way to gadolinium. Some of the links are funny, some are tenuous, and a lot refer to fascinating bits of chemistry trivia.

It seemed a shame not to preserve the final thread somehow. Each of the entries below is headed with a link to the original tweet — just in case you’d like to find, and follow, the thread yourself.

Without further ado, we present to you…

A meandering stroll around 118 elements

@Mark_Lorch
Hey folks! Who’s up for an element association game for in . The rules: I’ll start with an element, you reply with a story/factoid that links it to another element and so on… No repeats!

An atom of Mendelevium, atomic number 101 (from Wikimedia Commons)

@Mark_Lorch
It’s only fitting to start with number 101 Mendelevium

@Sciencenotscary
Mendeleev designed the first periodic table, which contains every other element, including <spins random number generator> #52, tellurium <blink> I swear that was random.

@Stare_at_Air
That feels a bit like cheating! But tellurium was first discovered in gold ore from Zlatna (a Romanian town named after the Slavic term for gold).

@RyeSci
Gold is one of those lovely elements known to the ancients with a symbol accordingly, Au. My favourite of those is Mercury, Hg from Hydrargyrium or liquid silver Hg.

@chronicleflask
Mercury has a v low MP because its electronic config, [Xe] 5d10 6s2, has all full shells — so it doesn’t form the +ve metal ions & delocalised electrons bonding system as other metals. Also quantum. Zn (zinc) has a low MP for the same reason.
(Side note: see this article for more info on mercury’s liquidity https://www.chemistryworld.com/news/relativity-behind-mercurys-liquidity/6297.article)

@allisontau
Zinc is element 30. Zinc rhymes with sink. If your kitchen sink is broken you call a plumber. Plumbers are called plumbers after plumbum, the Latin word for the element lead (Pb), because the Romans used lead to make pipes.

@Mark_Lorch
Lead in Greek is μολυβδος – Molyvdos which gives use the name of element 42, molybdenum.

bacteria@chronicleflask
Molybdenum-containing enzymes are found in bacteria: the simplest and oldest of the living organisms. Living organisms on planet Earth have carbon-based biology. (Time for some non-metals, I thought!)

@Stare_at_Air
This could be taken in so many directions based on carbon‘s chemistry, but I’ll ruin it — carbon reminds me of “Carboniferous”, which sounds like it should have something to do with iron (it doesn’t).

@sciencenotscary
Iron is in the same column of the periodic table as ruthenium, which usually means it should have similar reactivity and chemical behaviour, but it turns out iron is actually completely useless as a catalyst and will not get you a PhD.

@SuperScienceGrl
I’ve had a couple of people mistake my cat’s name, RuPhos, for something to do with ruthenium – it really isn’t, it’s a phosphorus ligand.

@Mark_Lorch
Phosphorus was first extracted from urine by Hennig Brandt in 1669. Later is was discovered that bone is calcium phosphate, which made for a ready supply to feed the match industry.

@David_S_Bristol
Calcium and phosphorous combine in bone along with a substantial amount of magnesium. ~60% of magnesium in the body is in bone. It is essential for a healthy skeleton and reduced magnesium is linked to osteoporosis.

@Stare_at_Air
Magnesium is a key component of Grignard reagents. Grignard shared his Nobel Prize with Sabatier, who in turn received it for his method of hydrogenating organic compounds. Hydrogen.

@drdelusional
Hydrogen, the lightest element, forms the majority of the mass of the Universe. This odorless and tasteless gas combines with Fluorine to result in hydrogen fluoride, a highly reactive acid.
(Side note: corrosive, not (especially) reactive.)

@WildCation
Electronegativity generally increases from left to right across a period, and generally decreases from top to bottom. Fluorine is the most electronegative element on the Pauling electronegativity scale. The LEAST electronegative element is (probably) caesium.

@chronicleflask
Ooh, ooh: Robert Bunsen (he of the burner) and Gustav Kirchhoff discovered two alkali metals, cesium and rubidium, in 1860.

@Stare_at_Air
Rubidium is one of several elements named after a colour (in this case the red lines seen in the emission spectrum), but chromium is associated with so many different colours it’s just named after the Greek word for colour, χρῶμα.

@Mark_Lorch
Amongst the Terracotta warriors were found what appears to be chrome (chromium) plated bronze swords. The alloy was mostly copper and tin, but also contained magnesium, nickel and cobalt.

@sumants
Cobalt is named from ‘kobold’, German for ‘goblin’. This comes from German miners – who were harvesting (cobalt) blue pigments – naming ores ‘goblin ores’ due to the effects of arsenic poisoning when the ores were smelted.

@WildCation
The use of Scheele’s Green, a popular green arsenic-based pigment, caused poisonings in the 19th century from its use in wallpaper, candles, even food. Similarly, in the 1920s, the “Radium Girls” developed cancer from painting watch faces with radium-based pigment.

@Mark_Lorch
Radium was discovered by Marie and Pierre Curie when they extracted it from Uraninite ore. From the same ore they extracted another element which they initially called radium-F. Later Marie renamed if after her home country – Poland. Giving us … Polonium.

@Stare_at_Air
I think the f-block is feeling a bit unloved, so let’s go from the elements that the Curies discovered (Polonium) to the one named after them. Curium.

@ndbrning
Curium is (possibly) the heaviest naturally occurring element (see here: https://www.nature.com/articles/s41557-018-0190-9). The other possible candidate is plutonium.

@Stare_at_Air
Plutonium was indirectly named by a child (the name Pluto for the planet was suggested by an 11-year-old girl). The only other element named by a child is neon, suggested by Ramsay’s son.

@Mark_Lorch
William Ramsay (neon) was also the first person to isolate helium. Prior to this is was known to exist from the spectra of the Sun. Hence the element’s name from Helios… Helium.

@DrMLHarris
Inhaling helium makes your voice squeaky. What happens if you inhale xenon? Researchers at a prestigious US lab decided to find out. Turns out, “heavier than air”=”too heavy for lungs to expel”. The experimenter’s life was saved when he stood on his head.
(Side note: watch what happened when Dr Bunhead of Brainiac tried the same thing.)

@FioraAeterna
Xenon is a really unusual element. In fact, it’s the only pure element that is also a general anesthetic! Yet it’s an unreactive noble gas. Weird, huh? For weird reasons, both Xenon and Argon are now on the anti-doping banned chemicals list.

@Stare_at_Air
People are often surprised to find that the third most abundant gas in the Earth’s atmosphere is Argon. Perhaps similarly surprising is that the third most abundant element in the universe as a whole (at least as far as we know) is oxygen.

@Mark_Lorch
Oxygen is a paramagnetic. If you condense some (it’s a beautiful pale blue liquid) and then place a neodymium magnet above the surface the oxygen jumps up onto the magnet. https://www.youtube.com/watch?v=bQKVt27SUR0&feature=youtu.be&t=91

@sumants
Neodymium was originally mined as a twinned material known as didymium. Carl Auer von Welsbach fractionally distilled didymium to isolate neodymium (new twin) and the other “green twin”, praesodymium.

@Stare_at_Air
“Green twin” in Greek (πράσινος and δίδυμος) is the base for the name of praseodymium — meanwhile “green twig” in Greek (θαλλός) is the base for the name of thallium, after the bright green spectral line used to identify it.

@sumants
Thallium was extremely popular as a poison in the early 20th century, but it’s mostly banned today. As a rat poison, it worked because it inhibited proteins that contained cysteine, an amino acid that contains… Sulphur.

@ndbrning
Sulfur
is responsible for the tarnishing of silver. The black tarnish is silver sulfide, caused by the metal’s reaction with small amounts of hydrogen sulfide in the air.

@Mark_Lorch
To clean your silver spoons put them in hot water with bicarb of soda & aluminium foil. The bicarb removes the aluminium oxide layer. This leaves the aluminium free to react with the silver sulfide, giving aluminium sulfide & clean silver.

@Stare_at_Air
What is still often called “tin foil” is nowadays almost always made from alumin(i)um. But it used to be made exclusively from tin until the early 20th century (first Al foil came around in 1910, but it took a few decades for it to replace Sn foil).

@sciencenotscary
Tin has two allotropes, a metallic one and a powder. It converts to the powder at Russian-winter temperatures. Napoleon’s troops had tin buttons on their jackets, which then wouldn’t close, and they died of exposure. Russia is the home of Dubna. Dubnium.

@ndbrning
One of the originally proposed names for Dubnium was Nielsbohrium, after Danish nuclear physicist Niels Bohr. Though this proposal wasn’t accepted, Bohr did eventually get an element named after him: element 107, bohrium.

@sumants
One of the two groups to have claimed discovery of bohrium in 1976 was led by Soviet scientist Yuri Oganessian, in whose honour we now have… Oganesson.

@robcarrphoto
Only 5 to 6 atoms of Oganesson have ever been detected. Originally thought to be a gas, computational chemistry revealed it would be a solid due to relativistic effects. Special & General Relativity were discovered by Albert Einstein, for whom Einsteinium was named.

@Stare_at_Air
Einstein (Einsteinium) famously developed his theory of relativity while working at the patent office. The first element to be patented was Americium.

@Mark_Lorch
Americium is created by bombarding uranium or plutonium with neutrons. It was first made by Seaborg (from Berkeley) in 1944 as part of the Manhattan project. Soooo many ways to go from here, but I’m going with… Seaborgium.

@Stare_at_Air
Shortly after the ACS announced 106 to be Sg (Seaborgium) in 1994, resolved not to allow names based on living people. Until it gave way about a year later, the IUPAC name for 106 was rutherfordium. In 1997, this name was instead assigned to element 104… Rutherfordium.

@chronicleflask
Rutherfordium was named after Ernest Rutherford, prob. most famous for the Rutherford atomic model developed after Geiger & Marsden’s gold foil expt. But he also carried out research into nuclear reaction bet. nitrogen & alpha particles.

@sciencenotscary
Nitrogen is usually thought of as being mostly inert an unreactive, until you make it an azide. Sodium azide is what inflates your car’s airbag in time to stop your head smacking the steering wheel.

@Mark_Lorch
After my grandpa died I helped clear his flat, over the years he had stashed various chemicals including 1/2kg of Na (sodium), KCN & conc HCl. To this day I shudder to think what might have been if I hadn’t been there to stop my family chucking it all down the sink. Chlorine.
(Side note: read more about that story here http://www.chemistry-blog.com/2013/04/18/chemical-nostalgia-my-grandfathers-lethal-legacy/)

@robcarrphoto
In organic chemistry lab, we used a lot of HCl (chlorine) of organic reactions, making salts, etc. But when I think of the Chemistry building, I think of bromine. The building smelled like bromine. The set of Beilstein books smelled like bromine.

@Mark_Lorch
Two of the elements stink. Bromine means “stench” and osmium means “smells”.

@ndbrning
Osmium is used in an alloy to make the tips of fountain pens hard and wear-resistant. In the past, iridium was used for this purpose, and sometimes the tipping material is still referred to as ‘iridium’ despite the element’s absence.

@Stare_at_Air
Not only was iridium discovered in the residue from trying to dissolve (impure) platinum, but Pt-Ir alloys are very useful, being both hard and chemically stable. The prototype kilogram is made of Pt-Ir, though a new definition of the kg comes in in May.

@sumants
The Pt-Ir (platinum) alloy was also used to make the prototype meter bar, which was replaced by a measure based on an electron transition within a Kr-86 atom. Krypton.

@sumants
While we’re going on about defining lengths, the Kr-86 (krypton) standard also redefined the ångström as 0.1nm, making obsolete the previous reference based on the spectral line of… cadmium.

@ndbrning
Cadmium is used in nickel-cadmium (Ni-Cd) rechargeable AA batteries. Due to cadmium’s toxicity, their sale has been banned in the EU for most purposes since 2006. They’ve been supplanted by another type of nickel-based battery, nickel metal hydride (NiMH).

@drdelusional
Breithauptite or NiSb (nickel) is a pale copper red colored mineral named after Johann Friedrich August Breithaupt, a Saxon Mineralogist. Antimony.

@chronicleflask
Antimony compounds have been powdered for use in medicine and cosmetics for thousands of years, often known by the Arabic name, kohl. Titanium dioxide is another common additive in makeup and sunscreens.

@Mark_Lorch
Titanium
 causes no immune response, making it an ideal material for implants. However it does slowly corrode in the body. A ceramic made of zirconia (zirconium dioxide) doesn’t suffer from this problem and is now commonly used for dental implants. Zirconium.

@drdelusional
Zirconium alloys are mainly used in nuclear reactors, however these alloys should not contain Hafnium.
(Side note: see this article for more info as to why http://www.iloencyclopaedia.org/part-ix-21851/metals-chemical-properties-and-toxicity/63/zirconium-and-hafnium)

@Stare_at_Air
Hafnium is one of two elements whose name is based on the Latin form of a Scandinavian capital — Hafnia is Copenhagen, while Holmia is Stockholm. Holmium.

@sumants
While working with erbia (grounds for a whole fascinating fork!), Per Cleve isolated two oxides, one which he called holmia (holmium oxide), and the other, thulia, which was identified as thulium oxide. Thulium.

@sumants
Thulium is commonly found in a mineral known as gadolinite, which is named after Johan Gadolin. While it doesn’t have much gadolinium in it, Gadolin wrongly thought a white metal he found in it was aluminium, and not… Beryllium.

@ndbrning
Beryllium is found in the mineral beryl, which emerald and aquamarine are precious forms of. One of the rarest varieties, red beryl, gets its colour from the presence of small amounts of manganese.

@chronicleflask
Manganese is used in REDOX titrations; the colour change from VII (dark purple) to II (pale pink) is very obvious. It’s commonly used to determine the amount of iron present. Another species that turns up in REDOX titrations is iodine/iodide.

@sciencenotscary
Iodine can occur in the form HIO4, periodic acid, which looks like the word for the table we’re talking about but is actually per-iodic. A metallic compound with a very similar electronic structure is perhenate, based on rhenium.

@ndbrning
Rhenium was (possibly) first discovered by Masataka Ogawa in 1908, though he thought he’d discovered element 43, technetium (which wasn’t actually discovered until 1937).

@sciencenotscary
One of only two cis-uranic elements with no stable isotopes, it (technetium) had to be synthesised to be discovered (hence the name). The other one is protactinium.

@ndbrning
The first long-lived isotope of protactinium was discovered by Otto Hahn and Lise Meitner in 1917. 80 years later, in 1997, Meitner became one of only 16 scientists to have an element named after them… Meitnerium.

@MrVanOosterhout
Meitnerium was first produced by German nuclear researchers in 1982, who bombarded a bismuth sample with iron ions. A week of bombardment produced a single meitnerium ion, which lasted all of five milliseconds before decaying.

@chronicleflask
The name bismuth dates from around the 1660s, and it’s unclear where it came from, but maybe from Old High German hwiz (“white”). Like water, liquid bismuth is denser than solid, a characteristic it also shares with the element germanium.

@Stare_at_Air
The name germanium proved controversial, sounding like geranium. Jokingly, angularium was proposed, hiding a translated form of the discoverer’s name (Winkler). Lecoq denied doing something similar when naming gallium (Gaul, but also gallus = rooster).

@drdelusional
Gallium is a low melting solid (melting point ~30°C) and it combines with selenium to form Gallium Selenide which finds applications in nonlinear optics.

@sumants
Selenium was identified by Berzelius and Gahn from pyrite found in the Falun mine in Sweden, which is one of the world’s largest repositories of Copper.

@Mark_Lorch
Eight elements were first isolated from rocks quarried in a the small village of Ytterby in Sweden (same country as copper mine). Four of those elements are named in tribute to the village (ytterbium, erbium, terbium, yttrium)… Ytterbium.

@Stare_at_Air
Near the Ytterby (ytterbium) mine is this sign, discussing Gadolin’s work and the elements found there. It talks about a “tung, svart sprängsten” (in this case the black, heavy gadolinite), but it just reminded me of the origin of the name tungsten!

@drdelusional
A compound of Tungsten, Potassium tungsten oxide, is used in solar energy and water treatment applications… Potassium.

@DrMLHarris
Potassium comes in both fermionic and bosonic isotopes, making it ideal for the study of both Bose-Einstein condensation and cold Fermi gases. Lithium also has this property.

@DrMLHarris
The first molecular Bose-Einstein condensate was created in 2003 by pairing up atoms of fermionic lithium-6 (lithium) to make bosonic Li2 molecules. Fermions are, of course, named after the physicist Enrico Fermi, who also has an element named after him... Fermium.

@sumants
Fermium was discovered in the fallout from a nuclear test, as was einsteinium when some filter papers were exposed to the same fallout. The work happened at the University of California, Berkeley, after which place we have… Berkelium.

@sumants
Berkelium is now synthesized mainly in the Oak Ridge National Laboratory in Tennessee, after which state, we have Element 117… Tennessine.

@DrMLHarris
Tennessine itself was synthesized at the Joint Institute for Nuclear Research in Dubna, Russia. The many contributions of this institute to the Periodic Table were recognized in the name of Element 115… Moscovium.

@sumants
Moscovium naturally underwent alpha emission and created… Nihonium.

DrMLHarris
Nihonium was named after the country where it was discovered, Japan. The discoverers expressed hope that this honour would help the country’s trust in science recover after the meltdown of the reactor at Fukushima, which uses uranium as fuel.

@sumants
Uranium, of course, is named after the planet Uranus. It probably makes sense, then, that its neighbour would be named after the planet’s neighbour, Neptune… Neptunium.

@Stare_at_Air
Despite many previous false claims of having produced element 93, including by Fermi, neptunium was first produced by McMillan and Abelson, at Berkeley Lab (yes, Berkeley again, of course), based in the state of California… Californium.

@sumants
Californium was first synthesized at the Lawrence Berkeley NL, which is named after Ernest Lawrence, after whom we have… Lawrencium.

@Mark_Lorch
Lawrencium is the final member of the actinides. Although it is arguably a member of group 3 along with scandium, yttrium, and lutetium… Scandium.

@sumants
When Mendeleev placed scandium in his periodic table, he had previously predicted its existence, which Per Cleve eventually confirmed. He named it eka-boron, since it would have been similar in its properties to… Boron.

@sumants
Borosil is a brand name that makes borosilicate glass, which is made from a compound oxide of boron and… Silicon.

@DrMLHarris
The A3B group of compounds (A=transition metal, B=anything) wasn’t considered particularly interesting until vanadium silicide, V3Si, (silicon) was found to act as a superconductor at 17K – one of the first Type II superconductors to be discovered… Vanadium.

@chronicleflask
Vanadium is famous for its many colours and oxidation states. The ability to readily change oxidation state makes it a good catalyst, notably for the contact process, used to make sulfuric acid. Another element which is used in catalysis is rhodium.

@ndbrning
Rhodium is used in catalytic converters in cars to remove nitrogen oxides, carbon monoxide, and unburnt hydrocarbons. Other metals used as catalysts in these converters are platinum and palladium.

@DrMLHarris
In 1989 Pons & Fleischmann claimed to have observed cold fusion via electrolysis of heavy water on a palladium electrode. That was false, but controlled hot fusion in tokamaks is real. Tokamaks use superconducting wire made from an alloy of tin and… Niobium.

@sumants
Niobium is named after Niobe from Greek mythology, and unsurprisingly, the next element one period down is named for her father, Tantalus… Tantalum.

@Mark_Lorch
Tantalum is one of those elements that was discovered in the rocks of Ytterby. Which gives its name to 4 elements, including … erbium.

@sumants
Along with ytterbium and erbium, the same rocks near Ytterby also yielded… terbium.

@DrMLHarris
Today’s main source of Terbium, however, is a mineral called bastnasite, which is named after yet another Swedish mine, Bastnas. This mineral is also a major source of… Cerium.

@Stare_at_Air
Cerium is named after Ceres, a dwarf planet hypothesised to contain an ocean of liquid water. A similar ocean is thought to exist inside Europa, the Jovian moon, named after the figure in Greek mythology. Also named after it is Europe… Europium.

@sumants
Europium(III) oxide is used to activate yttrium phosphors, mostly to create red on television and computer screens. Yttrium is also one of the elements to come out of the Ytterby mine.

@sciencenotscary
Like Yttrium, Indium is also used in screens because of its importance as a component of the semiconductor indium tin oxide.

@ndbrning
Radioactive indium ions have been investigated by researchers for their potential use in radiopharmaceuticals for diagnosis and treatment of tumours. Radioactive actinium ions have been investigated for the same purpose.

@mrfarabaugh
Actinium assumes oxidation state +3 in nearly all its chemical compounds. The Ac(III) ion has an electron configuration that is isoelectronic with Radon.

@sciencenotscary
Radon, being inherently radioactive, is a nuisance background for sensitive particle detectors. Another nuisance is thorium.

@Stare_at_Air
Thorium is named after Thor, the Norse god of thunder, on whom characters in many a comic have been based over the years. Prometheus, a Titan from Greek mythology, has also made an appearance in several comics and gives his name to element 61… Promethium.

@Mark_Lorch
Henry Moseley showed that atomic numbers corresponded to a physical property of the elements. Using this he found that some atomic numbers had no known elements: the gaps were 43, 61 (promethium), 72, 75, 85 (astatine), and 87.

@Stare_at_Air
All the group 17 elements up to and including astatine (“unstable”) are named after their properties (Ts ruined it), but many elements in the rest of the table are too. We still have two of these left — one of them is “hard to get” (though stable)… Dysprosium.

@Mark_Lorch
(Dysprosium) And the other is Barium which is derived from mineral baryte in which it is found. This in turn comes from the Greek βαρύς (barys) meaning heavy.

@DrMLHarris
Even heavier than barium, and much harder to obtain due to its half-life of just 22 minutes, the next element has never been observed in bulk, though like the other alkalis it has been laser cooled and trapped. Step up… Francium.

@Mark_Lorch
Marguerite Catherine Perey (a student of Marie Curie) discovered Francium and named if after her home country. France gets another hat tip in the table in the form of Lutecium which is named from the latin for Paris.

@DrMLHarris
(Lutecium) Another Paris-based discoverer was Paul-Émile Lecoq de Boisbaudran. He discovered three elements. Two of them, gallium and dysprosium, have been done already, but the third was… Samarium.

@DrMLHarris
De Boisbaudran is credited as Samarium‘s discoverer, but a different French chemist, Eugène-Anatole Demarçay, actually isolated the pure metal. Demarçay destroyed his eyesight in a chemical explosion. The godfather of explosive chemistry is Alfred Nobel… Nobelium.

@Stare_at_Air
Nobel (Nobelium) may have set up the Nobel prize because he was worried about being remembered for his contribution to developing more effective weapons. Georgy Flyorov also played a role in weapons research, as he encouraged Stalin to start an atomic bomb project… Flerovium.

@DrMLHarris
(Flerovium) The most dangerous isotope in nuclear fallout, the hazards of which helped to persuade the US, UK and Soviet Union to ban above-ground weapons tests, is strontium-90, which is taken up in the bones… Strontium.

@sumants
One of the popular electrode materials in solid oxide fuel cells is LSM, which is a perovskite (ABO3) in which B positions have Mn, and A slots are occupied by strontium and… Lanthanum.

@DrMLHarris
The name “lanthanum” derives from the Ancient Greek for “to lie hidden.” X-rays are also good at revealing hidden things, from broken bones to chemical structures to black holes. They were discovered by Wilhelm Roentgen, who is honoured with Element 111… Roentgenium.

@sumants
Roentgenium was first created at the Helmholtz Centre for Heavy Ion Research in Darmstadt, from which we have… Darmstadtium.

@sumants
Several elements have been synthesized/discovered at the Helmholtz Center, including meitnerium, roentgenium, darmstadtium, bohrium, and… Hassium.

@sumants
(Hassium) I left out one more element synthesized at the Helmholtz Center: Copernicium.

@sumants
(Copernicium) The Helmholtz Center also helped confirm Element 116, which had been created partly in Dubna, and partly at the Lawrence Livermore NL, after which it was named: Livermorium.

@DrMLHarris
(Livermorium) All of these reactors used to discover ultra-heavy elements require good shielding against radioactivity. Because of its high neutron cross section, one of the elements used in shielding is… Gadolinium.

@Mark_Lorch
YEH!!! 👏 🥳 🎉 That was great fun! Thanks for playing! I honestly wondered if that was even doable!
#ElementTales

Periodic Table by Andy Brunning of Compound Interest (click for more)


Special thanks to Andrea Chlebikova (@Stare_at_Air) for keeping track of which elements had and hadn’t been covered as we went along.

You can also read an article about this project, published in Physics World, by Margaret Harris (@DrMLHarris).

Further thanks to: Mark Lorch, Andrea Chlebikova, Andy Brunning, Steve Maguire, Michael Farabaugh, Margaret Harris and Sumant Srivathsan. Follow the Twitter handle links to find these lovely people and give them a follow.

2019: The Year of the Periodic Table

The Periodic Table

2019 is the International Year of the Periodic Table

In case you missed it, 2019 is officially the International Year of the Periodic Table, marking 150 years since Dmitri Mendeleev discovered the “Periodic System”.

Well, this is a chemistry blog, so it would be pretty remiss not to say something about that, wouldn’t it? So, here’s a really quick summary of how we got to the periodic table we all know and love…

Around 400 BCE, the Greek philosopher Democritus (along with a couple of others) suggested that everything was composed of indivisible particles, which he called “atoms” (from the Greek atomos). The term ‘elements’ (stoicheia) was first used around 360 BCE by Plato, although at that time he believed matter to be made up of tiny units of fire, air, water and earth.

Skipping over a few centuries of pursuing what was, we know now, a bit of a dead-end in terms of the whole earth, air, fire and water thing, in 1661, Robert Boyle was probably the first to state that elements were the building blocks of matter and were irreducible but, and this was the crucial bit, that we didn’t know what all the elements were, or even how many there might be.

Antoine Lavoisier wrote one of the first lists of chemical elements.

Antoine Lavoisier (yep, him again) wrote one of the first lists of chemical elements, in his 1789 Elements of Chemistry. He listed 33 of them, including some that turned out not to be elements, such as light.

Things moved on pretty quickly after that. Just thirty years later, Jöns Jakob Berzelius had worked out the atomic weights for 45 of the 49 elements that were known at that point.

So it was that by the 1810s, chemists knew of 50 or so chemical elements, and had atomic weights for most of them. It was becoming clear that more elements were going to turn up, and the big question became: how do we organise this ever-increasing list? It was a tricky problem. Imagine trying to put together a jigsaw puzzle where two-thirds of the pieces are missing, there’s no picture on the box, and a few pieces have been tossed in from other puzzles for good measure.

Enter Johann Döbereiner, who in 1817 noticed that there were patterns in certain groups of elements, which he called triads. For example, he spotted that lithium, sodium and potassium behaved in similar ways, and realised that if you worked out the average atomic mass of lithium and potassium, you got a value that was close to that of sodium’s. At the time he could only find a few triads like this, but it was enough to suggest that there must be some sort of structure underlying the list of elements.

In 1826 Jean-Baptiste Dumas (why do all these chemists have first names starting with J?) perfected a method for measuring vapour densities, and worked out new atomic mass values for 30 elements. He also set the value for hydrogen at 1, in other words, placing hydrogen as the “first” element.

Newland’s table of the elements had “periods” going down and “groups” going across, but otherwise looks quite familiar.

Next up was John Newlands (another J!), who published his “Law of Octaves” in 1865. Arranging the elements in order of atomic mass, he noticed that properties seemed to be repeating in groups of eight. His rows and columns were reversed compared to what we use today — he had groups going across, and periods going down — but apart from that the arrangement he ended up with is decidedly familiar. Other chemists, though, didn’t appreciate the musical reference, and didn’t take Newlands very seriously.

Which brings us, finally, to Dmitri Mendeleev (various other spellings of his name exist, including Dmitry Mendeleyev, but Dmitri Mendeleev seems to be the most accepted one). His early life history is a movie-worthy story (I won’t go into that else we’ll be here all day, but check it out, it’s really quite amazing). When he was just 35 he made a formal presentation to the Russian Chemical Society, titled The Dependence between the Properties of the Atomic Weights of the Elements, which made a number of important points. He noted, as Newlands had already suggested, that there were repeating patterns in the elements, or periodicity, and that there did indeed seem to be connections between sequences of atomic weights and chemical properties.

Dmitri Mendeleev suggested there were many elements yet to be discovered.

Most famously, Mendeleev suggested that there were many elements yet to be discovered, and he even went so far as to predict the properties of some of them. For example, he said there would be an element with similar properties to silicon with an atomic weight of 70, which he called ekasilicon. The element was duly discovered, in 1886 by Clemens Winkler, and named germanium, in honor of Germany: Winkler’s homeland. Germanium turns out to have an atomic mass of 72.6.

Mendeleev also predicted the existence of gallium, which he named ekaaluminium, and predicted, amongst other things, that it would have an atomic weight of 68 and a density of 5.9 g/cm3. When the element was duly discovered by the French chemist Paul Emile Lecoq de Boisbaudran, he first determined its density to be 4.7 g/cm3. Mendeleev was so sure of his prediction that he wrote to Lecoq and told him to check again. It turned out that Mendeleev was right: gallium’s density is actually 5.9 g/cm3 (and its atomic weight is 69.7).

Despite constructing the one thing that every chemist over the last 150 years has spent years of their life poring over, Mendeleev was never awarded the Nobel Prize for Chemistry. He was nominated in 1906, but the story goes that Svante Arrhenius — who had a lot of influence in the Royal Swedish Academy of Sciences — held a grudge against Mendeleev because he’d been critical of Arrhenius’s dissociation theory, and argued that the periodic system had been around for far too long by 1906 to be recognised for the prize. Instead, the Academy awarded the Nobel to Henri Moissan, for his work on isolating fluorine from its compounds (no doubt impressive, not to mention dangerous, chemistry).

Henry Moseley

Henry Moseley proposed that atomic number was equal to the number of protons in the nucleus of an atom.

Mendeleev died in 1907 at the age of 72, just before the discovery of the proton and Henry Moseley’s work, in 1913, which proposed that the atomic numbers of elements should be equal to the number of positive charges (protons) they contained in their nuclei. This discovery would have pleased Mendeleev, who had already suggested, based on their properties, that some elements shouldn’t be placed in the periodic table strictly in order of atomic weight.

After which, of course, came the discovery of the neutron — which would finally clear up the whole atomic mass/atomic number thing — atomic orbital theory, and the discovery of super-heavy elements. The most recent additions to the modern periodic table were the official names, in 2016, of the final four elements of period 7: nihonium (113), moscovium (115), tennessine (117) and oganesson (118).

Which brings us up to date. For now…


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What is Water? The Element that Became a Compound

November 2018 marks the 235th anniversary of the day when Antoine Lavoisier proved water to be a compound, rather than an element.

I’m a few days late at the time of writing, but November 12th 2018 was the 235th anniversary of an important discovery. It was the day, in 1783, that Antoine Lavoisier formally declared water to be a compound, not an element.

235 years seems like an awfully long time, probably so long ago that no one knew anything very much. Practically still eye of newt, tongue of bat and leeches for everyone, right? Well, not quite. In fact, there was some nifty science and engineering going on at the time. It was the year that Jean-François Pilâtre de Rozier and François Laurent made the first untethered hot air balloon flight, for example. And chemistry was moving on swiftly: lots of elements had been isolated, including oxygen (1771, by Carl Wilhelm Scheele) and hydrogen (officially by Henry Cavendish in 1766, although others had observed it before he did).

Cavendish had reported that hydrogen produced water when it reacted with oxygen (known then as inflammable air and dephlogisticated air, respectively), and others had carried out similar experiments. However, at the time most chemists favoured phlogiston theory (hence the names) and tried to interpret and explain their results accordingly. Phlogiston theory was the idea that anything which burned contained a fire-like element called phlogiston, which was then “lost” when the substance burned and became “dephlogisticated”.

Cavendish, in particular, explained the fact that inflammable air (hydrogen) left droplets of “dew” behind when it burned in “common air” (the stuff in the room) in terms of phlogiston, by suggesting that water was present in each of the two airs before ignition.

Antoine-Laurent Lavoisier proved that water was a compound. (Line engraving by Louis Jean Desire Delaistre, after a design by Julien Leopold Boilly.)

Lavoisier was very much against phlogiston theory. He carried out experiments in closed vessels with enormous precision, going to great lengths to prove that many substances actually became heavier when they burned and not, as phlogiston theory would have it, lighter. In fact, it’s Lavoisier we have to thank for the names “hydrogen” and “oxygen”. Hydrogen is Greek for “water-former”, whilst oxygen means “acid former”.

When, in June 1783, Lavoisier found out about Cavendish’s experiment he immediately reacted oxygen with hydrogen to produce “water in a very pure state” and prove that the mass of the water which formed was equal to the combined masses of the hydrogen and oxygen he started with.

He then went on to decompose water into oxygen and hydrogen by heating a mixture of water and iron filings. The oxygen that formed combined with the iron to form iron oxide, and he collected the hydrogen gas over mercury. Thanks to his careful measurements, Lavoisier was able to demonstrate that the increased mass of the iron filings plus the mass of the collected gas was, again, equal to the mass of the water he had started with.

Water is a compound of hydrogen and oxygen, with the formula H2O.

There were still arguments, of course (there always are), but phlogiston theory was essentially doomed. Water was a compound, made of two elements, and the process of combustion was nothing more mysterious than elements combining in different ways.

As an aside, Scottish chemist Elizabeth Fulhame deserves a mention at this point. Just a few years after Lavoisier she went on to demonstrate through experiment that many oxidation reactions occur only in the presence of water, but the water is regenerated at the end of the reaction. She is credited today as the chemist who invented the concept of catalysis. (Which is a pretty important concept in chemistry, and yet her name never seems to come up…)

Anyway, proving water’s composition becomes a lot simpler when you have a ready supply of electricity. The first scientist to formally demonstrate this was William Nicholson, in 1800. He discovered that when leads from a battery are placed in water, the water breaks up to form hydrogen and oxygen bubbles, which can be collected separately at the submerged ends of the wires. This is the process we now know as electrolysis.

You can easily carry out the electrolysis of water at home.

In fact, this is a really easy (and safe, I promise!) experiment to do yourself, at home. I did it myself, using an empty TicTac box, two drawing pins, a 9V battery and a bit of baking soda (sodium hydrogencarbonate) dissolved in water – you need this because water on its own is a poor conductor.

The drawing pins are pushed through the bottom of the plastic box, the box is filled with the solution, and then it’s balanced on the terminals of the battery. I’ve used some small test tubes here to collect the gases, but you’ll be able to see the bubbles without them.

Bubbles start to appear immediately. I left mine for about an hour and a half, at which point the test tube on the negative terminal (the cathode) was completely full of gas, which produced a very satisfying squeaky pop when I placed it over a flame.

The positive electrode (the anode) ended up completely covered in what I’m pretty sure is a precipitate of iron hydroxide (the drawing pins presumably being plated steel), which meant that very little oxygen was produced after the first couple of minutes. This is why in proper electrolysis experiments inert graphite or, even better, platinum, electrodes are used. If you do that, you’ll get a 1:2 ratio by volume of oxygen to hydrogen, thus proving water’s formula (H2O) as well.

So there we have it: water is a compound, and not an element. And if you’d like to amuse everyone around the Christmas dinner table, you can prove it with a 9V battery and some drawing pins. Just don’t nick the battery out of your little brother’s favourite toy, okay? (Or, if you do, don’t tell him it was my idea.)


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Effective elements: some great periodic tables

My all-time favourite scarf (made by Rooby Lane on Etsy from a periodic table by Science Notes)

I’m a chemist (no, really? I hear you cry) and like all chemists, I love the periodic table. Why do we love this weird grid of boxes and letters and numbers? Because it’s awesome, that’s why.

No, really, it is. Can physics or biology summarise pretty much everything important about their subject with one, single page of information? (Hint: nope.) But chemists have been able to do just that for the best part of 150 years.

The person we have to thank (mostly) for this brilliant bit of insight is one Dmitri Mendeleev. He was born in Siberia in February 1834 (there’s a bit of an issue with the exact date due to the Russian switch to the Gregorian calendar in 1918 but most sources seem to have settled on the 8th). He was the youngest of more than 10 children, but the really incredible bit about his story is that when he was just 15 years old his mother took him to Moscow, a journey of best part of 1000 miles. There were, at this time, some freshly-built stretches of railway, but make no mistake, it would’ve been a long and difficult trip.

Mendeleev’s mother wanted her youngest son to attend the University of Moscow. But when they got there, the University refused to accept him. So they moved on to the Main Pedagogical Institute in Saint Petersburg, which fortunately had more sense.

Mendeleev’s life is actually pretty colourful and makes for a great story (why is there no film??), but I won’t go into any more detail here, except to say that he gave a formal presentation on his periodic table of the elements in 1869. (Oh, and he also helped to found the first oil refinery in Russia, and did a lot of work on the technique of industrial fractional distillation, which literally no one ever seems to mention.)

So the periodic table is amazing, and if anything its creator was even more so. But what I actually want to do in this post is list some of my most favourite periodic table sites. There are few out there, and they contain a host of useful information above and beyond the standard atomic weight, atomic mass type-stuff. So, without further ado…

  • Sir Martyn Poliakoff recording for Periodic Videos

    Periodic Videos – produced by Nottingham University, this has a video for each element in the periodic table, including the newest ones. The videos all feature the gloriously-haired Sir Martyn Poliakoff and are great fun to watch.

  • Science Notes periodic tables – if you ever need a high-resolution periodic table, fancy making your laptop background into a periodic table (surprisingly handy, actually), or just want to refer to their simple-but-effective interactive version, this is a great place to start (my scarf, pictured above, was made from a print of Science Notes’ 118 Element Periodic Table Poster with Hubble Stars and Nebula). 
  • The Royal Society of Chemistry’s Periodic Table – particularly useful for students, as you can mouseover each element and key information such as electronic configuration appears in a little box on the same page – no clicking required. It’s really fast and easy to use. And if you do click on an element, a host of extra information appears above and beyond the usual history and uses, such as links to podcasts, videos and information about supply risk.
  • MPSE: Merck’s Periodic Table of the Elements – if you want a periodic table app for your mobile device, this is a great one. It’s quick to load to beautiful to look at. Available for Apple and Android devices.
  • Nature Chemistry: In Your Element – a periodic table of interesting and insightful essays (and I’m not just saying this because I wrote one of them) about the different elements.The most recent piece is on vanadium.
  • The Periodic Table of Tech – this one is particularly focused on what the elements are used for. You might learn, for example, that californium isotopes are used to detect landmines, or that zirconium isn’t just good for making cubic zirconia gems; it’s also used in nuclear fuel rods. What I particularly like about this is that it has all the information on one page, so it’s particularly easy to browse.

There will be many others which I haven’t mentioned. If you have a different favourite, do comment below!


Like the Chronicle Flask’s Facebook page for regular updates, or follow @chronicleflask on Twitter. All content is © Kat Day 2017. You may share or link to anything here, including the images, but you must reference this site if you do.


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Chemistry jokes get the best reactions

Today, 24th March, is Red Nose Day 2017 in the UK. I decided to see if I could collect some new chemistry jokes. There are some, of course, that we’ve all heard before – we might even say that all the best ones argon.

So, I promised to donate £10 if I got sent at least five new jokes. And I did! So I have! And here are my favourite five, in no particular order. Enjoy!

“I’ll tell you a joke about a tiny amount of iron for a small Fe.”@hullodave

“Chemistry Fact: There’s really no such thing as hydrogen. The inventor of the Periodic Table just needed a place to land a tiny helicopter.”@hullodave

“Why don’t they galvanise ships to stop corrosion? …That would make them zinc.”

“Do you know why everyone wants to work with bismuth? Because there’s no bismuth like showbismuth!” — @GriceChemistry

“I know a great long Justus Von Liebig joke but it needs condensing to get it on Twitter.” — 

If you’ve enjoyed these, if they’ve even so much as made you crack a little smile, please go and donate a couple of quid to Comic Relief. It’s a brilliant charity which helps people all over the world.

Donate here

The Chronicles of the Chronicle Flask: 2016

2016 is limping to its painful conclusion, still tossing out last-minute nasty surprises like upturned thumb tacks in the last few metres of a marathon. But the year hasn’t been ALL bad. Some fun, and certainly interesting, things happened too. No, really, they did, honestly.

So with that in mind, let’s have a look back at 2016 for the Chronicle Flask….

January kicked off with a particularly egregious news headline in a well-known broadsheet newspaper: Sugar found in ketchup and Coke linked to breast cancer. Turns out that the sugar in question was fructose. Yes, the sugar that’s in practically everything, and certainly everything that’s come from a plant. So why did the newspaper in question choose ketchup and Coke for their headline instead of, oh, say, fruit juice or honey? Surely not just in an effort to sell a few more newspapers after the overindulgent New Year celebrations. Surely.

octarineThere was something more lighthearted to follow when IUPAC  verified the discoveries of elements 113, 115, 117 and 118. This kicked off lots of speculation about the elements’ eventual names, and the Chronicle Flask suggested that one of them should be named Octarine in honour of the late Sir Terry Pratchett. Amazingly, this suggestion really caught everyone’s imagination. It was picked up in the national press, and the associated petition got over 51 thousand signatures!

In February I wrote a post about the science of statues, following the news that a statue to commemorate Sir Terry Pratchett and his work had been approved by Salisbury City Council. Did you know that there was science in statues? Well there is, lots. Fun fact: the God of metalworking was called Hephaestus, and the Greeks placed dwarf-like statues of him near their Hearths – could this be where the fantasy trope of dwarves as blacksmiths originates?

MCl and MI are common preservatives in cosmetic products

MCl and MI are common preservatives in cosmetic products

My skeptical side returned with a vengeance in March after I read some online reviews criticising a particular shampoo for containing a substance known as methylchloroisothiazolinone. So should you be scared of your shampoo? In short, no. Not unless you have a known allergy or particularly sensitive skin. Otherwise, feel free to the pick your shampoo based on the nicest bottle, the best smell, or the forlorn hope that it will actually thicken/straighten/brighten your hair as promised, even though they never, ever, ever do.

Nature Chemistry published Another Four Bricks in the Wall in April – a piece all about the potential names of new elements, partly written by yours truly. The month also brought a sinus infection. I made the most of this opportunity by writing about the cold cure that’s 5000 years old. See how I suffer for my lovely readers? You’re welcome.

In May I weighed in on all the nonsense out there about glyphosate (and, consequently, learned how to spell and pronounce glyphosate – turns out I’d been getting it wrong for ages). Is it dangerous? Nope, not really. The evidence suggests it’s pretty harmless and certainly a lot safer than most of its alternatives.

may-facebook-postSomething else happened in May: the Chronicle Flask’s Facebook page received this message in which one of my followers told me that my post on apricot kernels had deterred his mother from consuming them. This sort of thing makes it all worthwhile.

In June the names of the new elements were announced. Sadly, but not really very surprisingly, octarine was not among them. But element 118 was named oganesson and given the symbol Og. Now, officially, this was in recognition of the work of Professor Yuri Oganessian, but I for one couldn’t help but see a different reference. Mere coincidence? Surely not.

July brought another return to skepticism. This time, baby wipes, and in particular a brand that promise to be “chemical-free”. They’re not chemical-free. Nothing is chemical-free. This is a ridiculous label which shouldn’t be allowed (and yet, inexplicably, is still in use). It’s all made worse by the fact that Water Wipes contain a ‘natural preservative’ called grapefruit seed extract which, experiments have shown, only actually acts as a preservative when it’s contaminated with synthetic substances. Yep. Turns out some of Water Wipes claims are as stinky as the stuff they’re designed to clean up.

Maria Lenk Aquatic Enter, Tuesday, Aug. 9, 2016. (AP Photo/Matt Dunham)

Maria Lenk Aquatic Enter, Tuesday, Aug. 9, 2016. (AP Photo/Matt Dunham)

August brought the Olympics, and speculation was rife about what, exactly, was causing the swimming pools to turn such strange shades of green. Of course, the Chronicle Flask knew the correct solution…

August also saw MMS and CD reared their ugly heads on social media again. CD (chlorine dioxide) is, lest we forget, a type of bleach solution which certain individuals believe autistic children should be made to drink to ‘cure’ them. Worse, they believe such children should be forced to undergo daily enemas using CD solutions. I wrote a summary page on MMS (master mineral solution) and CD, as straight-up science companion to the commentary piece I wrote in 2015.

mugsSeptember took us back to pesticides, but this time with a more lighthearted feel. Did you know that 99.99% of all the pesticides you consume are naturally-occurring? Well, you do if you regularly read this blog. The Chronicle Flask, along with MugWow, also produced a lovely mug. It’s still for sale here, if you need a late Christmas present… (and if you use the code flask15 you’ll even get a discount!)

In October, fed up with endless arguments about the definition of the word ‘chemical’ I decided to settle the matter once and for all. Kind of. And following that theme I also wrote 8 Things Everyone Gets Wong About ‘Scary’ Chemicals for WhatCulture Science.

Just in case that wasn’t enough, I also wrote a chapter of a book on the missing science of superheroes in October. Hopefully we should see it in print in 2017.

Sparklers are most dangerous once they've gone out.

Sparklers are most dangerous once they’ve gone out.

I decided to mark Fireworks Night in November by writing about glow sticks and sparklers. Which is riskier? The question may not be as straightforward as you’d imagine. This was followed by another WhatCulture Science piece, featuring some genuinely frightening substances: 10 Chemicals You Really Should Be Scared Of.

And that brings us to December, and this little summary. I hope you’ve enjoyed the blog this year – do tell your friends about it! Remember to follow @ChronicleFlask on Twitter and like fb.com/chronicleflask on Facebook – both get updated more or less daily.

Here’s wishing all my lovely readers a very Happy New Year – enjoy a drop of bubbly ethanol solution and be careful with the Armstrong’s mixture…. 

See you on the other side!

new-year-1898553_960_720

What IS a chemical?

a_chemistry_teacher_explaining_an_experiment_8d41253v

You at the back there! Get your nose out of that dictionary and pay attention!

What do we mean when we use the word “chemical”? It seems like a simple enough question, but is it, really? I write about chemicals all the time – in fact my last WhatCulture article was about just that – and I’ve mentioned lots of different definitions before. But I’ll be honest, some of them have bothered me.

I don’t often like the definitions you find in dictionaries. Lexicography and chemistry don’t seem to be common bedfellows, and dictionary compilers haven’t, generally speaking, spent their formative years being incessantly nagged by weary chemistry teachers about their choice of vocabulary.

For example, in the Cambridge Dictionary we find:
any basic substance that is used in or produced by a reaction involving changes to atoms or molecules.”

Hm. Firstly, “basic” has a specific meaning in chemistry. Obviously the definition doesn’t mean to imply that acids aren’t chemicals, but it sort of accidentally does. Then there’s the implication that a chemical reaction has to be involved. So inert substances aren’t chemicals? Admittedly, “used in” doesn’t necessarily imply reacts – it could be some sort of inert solvent, say – but, again, it’s bothersome. Finally, “atoms or molecules”. Ionic substances not chemicals either, then?

Yes, it’s picky, but chemists are picky. Be glad that we are. A misplaced word, or even letter, on a label could have serious consequences. Trust me, you do not want to mix up the methanol with the ethanol if you’re planning cocktails. Similarly, fluorine is a whole other kettle of piranhas compared to fluoride ions. This stuff, excuse the pun, matters.

Dictionary definitions have their problems.

Dictionary definitions have their problems.

Let’s look at some more definitions (of the word as a noun):

The Free Dictionary tells us that a chemical is:
“A substance with a distinct molecular composition that is produced by or used in a chemical process.”

Merriam Webster says:
“of, relating to, used in, or produced by chemistry or the phenomena of chemistry <chemical reactions>”

And Dictionary.com goes with the simple:
“a substance produced by or used in a chemical process.”

That idea that a chemical reaction must be involved somehow seems to be pervasive. It’s understandable, since that’s the way the word is mostly used, but it’s not really right. Helium, after all, is still very much a chemical, despite being stubbornly unreactive.

Possibly the best of the bunch is found in the Oxford Living Dictionary:
“A distinct compound or substance, especially one which has been artificially prepared or purified.”

Not bad. Well done Oxford. No mention of chemical reactions here – it’s just a substance. We do most often think of chemicals as things which have been “prepared” somehow. Which is fair enough, although it can lead to trouble. In particular, ridiculous references to “chemical-free” which actually mean “this alternative stuff is naturally-occurring.” (Except of course it often isn’t: see this article about baby wipes.) The implication, of course, is that thing in question is safe(r), but there are lots and lots of very nasty chemicals in nature: natural does not mean safe.

You keep using that word. I do not think it means what you think it means.

Sometimes people will go the other way and say “everything is chemicals.” We know what this means, but it has its problems, too. Light isn’t a chemical. Sound isn’t a chemical. All right, those are forms of energy. What about neutrinos, then? Or a single proton? Or a single atom? Or, going the other way, some complicated bit of living (or once living) material? In one debate about this someone suggested to me that a “chemical was anything you could put in a jar,” at which point I pedantically said, “I keep coffee in a jar. Is that a chemical?” Obviously there are chemicals in coffee, it works from the “everything is chemicals” perspective, but it’s a single substance that’s not a chemical.

Language is annoying. This is why chemists like symbols and numbers so much.

Anyway, what have we learned? Firstly, something doesn’t necessarily have to be part of a chemical reaction to be a chemical. Secondly, we need to include the idea that it’s something with a defined composition (rather than a complex, variable mixture, like coffee), thirdly that chemical implies matter – light, sound etc don’t count, and fourthly that it also implies a certain quantity of stuff (we probably wouldn’t think of a single atom as a chemical, but collect a bunch together into a sample of gas and we probably would).

So with all that in mind, I think I shall go with:

So what IS a chemical?

A chemical is…

(Drum roll please….)

Any substance made of atoms, molecules and/or ions which has a fixed composition.

I’m not entirely convinced this is perfect, but I think it more or less works.

If you have a better idea, please do comment and let me know!


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