By John Emsley and Rob Sharp
It's a vital part of chemistry teachers' educational repertoire, as much as a scorched Bunsen burner or a sackful of safety goggles. With its array of digits and chemical abbreviations, it appears everywhere, from pencil cases to posters – and even inspired a book of short stories, The Periodic Table by Primo Levi (named by the Royal Institute as the best science book ever).
Whether you love chemistry or not, the modern periodic table, first successfully mapped out by Russian academic Dimitri Mendeleyev in 1869, occupies a coveted space in science-lovers' psyches. This traditional chart – with its odourless boredom of noble gases on the right, fizzing reactivity of transition metals in the middle – has persisted because of its efficient systematisation of a disparate array of elements.
But scientists, always eager to eke out a closer model of the truth, have been trying to improve it for 150 years. Online, it's easy to find periodic tables devised by researchers in spiral, three-dimensional, pyramidal and helical form – and that's just the experts. Amateur enthusiasts, meanwhile, obsessed by the table's design, have transferred Mendeleyev-inspired charts onto mugs, T-shirts, even toy elephants (though the latter is rather difficult to read). It's no coincidence that iPad champion-in-chief Stephen Fry has described the new "Elements" iPad app as alone worth the gadget's retail price. Released in Britain last month, the app's creators hope this country will take to it like the Americans, who have already bought 30,000 copies.
So why are we still so interested in the periodic table? "The standard physicists' criticism of chemists is that they are stamp collectors," says periodic table expert and "The Elements'" creator Theodore Gray. "That's because physicists think they study the fundamentals of what makes everything work. In their view, chemists just collect all of these manifestations of physics – the physical properties of elements – and don't concern themselves with what makes these things the way they are.
"But stamp collecting is a very popular hobby. It's fun to collect things. And the periodic table has a nice number of elements: around 100. It's a good number, and fits well with, say, a collection of beer or vegetables, which people have categorised using the periodic table's principles online. Also, people love it because it's universally known. It's like the Nike logo – everyone is familiar with its shape."
Mendeleyev's brain wave in fact followed on from hundreds of years of scientific research. In 1862 a French geologist, Alexandre de Chancourtois, had written a list of elements on a piece of tape, which he then wound around a cylinder. He noticed that chemically similar elements came below one another – in other words, the elements were "periodic" – and that as they grew in size, their properties repeated with regularity.
Around this time, in Russia Mendeleyev was throwing his intellectual heft behind the problem too. He wrote each of the elements on a different piece of card, along with their atomic weight and the formula of their compound with oxygen (their "oxide"). Like a game of Patience, he arranged the cutouts in order of weight, putting similar oxides in rows.
Then, his 'Eureka moment': he ascertained that there is an underlying system determining the elements' properties (the exact reasons for which has something to do with the sub-atomic arrangement of electrons – just about within the GCSE chemistry syllabus – hence periodic tables' ubiquity in classrooms). In the late 19th century, Mendeleyev reported his results to the Russian Chemical Society. He was so confident of his predictive powers that he foresaw the properties of aluminium, silicon and boron, which had not yet been discovered. His tabular creation featured around 60 elements. Compare that to the 118 now known.
Over the years, various groups of elements – such as the noble gases in the 1890s – were slotted into Mendeleyev's original outline as they were discovered. Such amendments have given scientists the excuse to see if they can go one better than Mendeleyev. One of the most popular alternatives is German philologist Theodor Benfey's two-dimensional spiral, conceived in 1960. This gets around one of the major limitations of Mendeleyev's table: the disproportionate distance between an element at the right-hand end of the table and the one in the row beneath it on the left-hand side.
Another researcher, Paul Giguere, has produced a three-dimensional table with the elements arranged according to the "energy levels" of atoms' electrons. It looks a little like a signpost with three different signs pointing in different directions. Most people keep coming back to Mendeleyev's original, however. For one, its convention of moving from left to right is something instinctive for readers in many languages.
"The basic problem is that the logical arrangement of these elements is not a two-dimensional form," continues Gray. "It's a hierarchical network essentially; but you need to be able to simplify it... Different people have different priorities. Chemists are interested in physical boiling points, physicists in electron arrangements. I find the debate silly.
"The standard shape is fine. It has problems, but so do all the other arrangements. The spiral is fine – but you don't have room for all the boiling points, or orbital configurations, which you get in the Mendeleyev table." He adds, however, "That said, the standard format has lanthanoids and actinoids at the bottom of the chart, held away from the other elements. They should really be incorporated into the middle of the table, but that would make it hard to fit the whole thing onto a reasonably sized piece of paper."
Where do we go from here? Well, it's probably no exaggeration to say that "The Elements" app marks the acme in periodic table presentation – so far. It's based on Gray's best-selling poster and book of the same name, and using it is something of a dream: you can search a high-resolution version of Mendeleyev's periodic table for whatever element you please. When you've found it, you can draw up three-dimensional rotating structures, read Gray's informatively written information on it, even investigate the material's current price on the stock market, sneak a peak at examples of their use in the real world, and study 3D images that "pop out" when special glasses are worn. "The sheer joy of being able to manipulate these little guys cannot be underestimated," says Boing Boing's Xeni Jardin in her breathless review, viewable on YouTube. "Why would you want paper when you can have this?"
Many of the more unusual periodic table designs – the helices, the spirals and such like – have been brought together by Salford-based chemist Mark Leach, who displays them on his website Meta-synthesis.com. His slew of arrangements hints at a hobby bordering on obsession.
Why does he do it? "For me, the appeal is simple. The periodic table is an icon of science that sits at the heart of chemistry," he says. "Everything in the physical world is constructed from periodic table stuff. In other words, the 92 stable chemical elements. While many people consider there to be one periodic table, actually there are many formulations. Many of the old versions seem strange today, so many are being invented. Since 2000, I've managed to upload more than 40 new forms to the database I run on my website. I've always had a long interest in how chemistry uses and grows out of the table."
And sites that have arranged comic books according to a loose interpretation of the periodic table's rules are evidence of the public's obsession. Why are so many amateurs sticking their splint into this creative flame? "Life makes sense in the periodic table," concludes British designer David Gray, owner of Oddhero, a graphic and typographic art company. "Designers love order, they love boxes. And when we get on a bit, there's time to get nostalgic about those bits of school we remember: letters, some stuff about triangles, periodic tables, dusty maps. We reuse them in our work, or get jobs where people pay us to make cool scribbles that look nice."
There's hope for all us laypeople yet, then. That familiar rectangular chart, with its intelligently designed weights, boiling points and atomic numbers, will always provide an elegant map to help us navigate our way towards scientific truth. Failing that, it'll definitely make a snazzy design for a coaster.