The periodic table is one of the most iconic images in science, a guide to the chemistry of our world. But it's only one among many visual ways to classify the elements.
There are thousands of alternative periodic tables or systems, some predating the invention of the now-standard version you might know from the school chemistry lab.
The earliest attempts to classify elements
The earliest attempts to classify matter, from metals to minerals, were based on the idea of essential qualities, or elements. Ancient Greek philosophers had four: air (hot and wet), water (cold and wet), earth (cold and dry) and fire (dry and hot).
Grouping chemical substances together according to similar qualities had practical value for alchemists and apothecaries, but there was no consensus or underlying order.
Things began to change at the end of the 18th century, as chemists introduced classification based on measurable quantities, like weight.
In 1789 one leading moderniser, the famed French chemist Antoine Lavoisier, produced a list of 33 ‘simple substances’ that made up the 300 or so chemicals known at the time, categorised by gases, metals, non-metals and earths.
John Dalton, a Manchester schoolteacher, introduced the idea of classifying elements by the relative weight of their atoms in 1806—a revolutionary concept at the time, which would be crucial to the invention of periodic tables.
Today we know of 118 elements that can be combined to form over 70 million different chemical compounds, so having a system to classify these at an elemental level is crucial.
What is a periodic table?
'Periodic' tables are named as such because they order elements in such a way that their chemical properties repeat periodically. after regular intervals.
The figure most closely associated with the periodic table is Dmitri Mendeleev, the Russian chemist who devised his first table in 1869.
It looks unlike the modern form we know today, as the elements are arranged by ascending weight downwards, rather than across.
But Mendeleev’s periodic table was not the first. There were five others before him.
The idea had been in the air since the first international conference of chemistry in 1860 at Karlsruhe, Germany. At this meeting, standard values for the atomic weights of the 60 elements then known had been agreed by the world's leading chemists.
Yet the first periodic pioneer was not a chemist.
What did the first periodic table look like?
In 1862 the French geologist Alexander-Emile Beguyer de Chancourtois published a paper describing a classification of the elements.
De Chancourtois’ ‘telluric screw’, as he called it, placed the elements in order of atomic weight in a spiral pattern around a cylinder.
Like Mendeleev’s table, but seven years before, de Chancourtois had stumbled upon a periodic repetition of chemical properties in his arrangement.
Unluckily for him, the groundbreaking paper escaped the attention of chemists for decades, largely because the publisher did not include a visual diagram of his screw system.
In 1926 the Science Museum made a working model of de Chancourtois' periodic screw.
By turning the handle, you can see chemical groupings of elements, such as lithium, sodium and potassium (three of the alkali metals), align vertically down the rotating column.
Atomic mass, weight or number?
- An element can come in different forms (isotopes), depending on how many neutrons it contains. Atomic weight is the average mass for an element across all its isotopes.
- Atomic mass is the mass of a particular atom or isotope.
- An element's atomic number is the number of protons it has. Atomic number replaced atomic weight as the value that determines the order of the elements in the periodic table.
Can periodic tables work in three dimensions?
The first periodic table—de Chancourtois’ screw—was not really a table at all, but a three-dimensional system for arranging the elements.
The defining feature that unites de Chancourtois’ screw with Mendeleev’s table and many others is the periodic pattern of chemical properties, which allows chemists to predict how elements behave and react according to their position in the system.
While it was Mendeleev’s two-dimensional table of rows and columns that became the standard form (confusingly, he always used the term ‘system’ over ‘table’), this did not discourage later chemists from introducing alternatives.
As well as being visually attractive, some three-dimensional periodic systems contained extra information about the elements.
See how de Chancourtois' system worked in practice:
What can alternative periodic systems tell us about the elements?
Perhaps the most important periodic system post-Mendeleev was a three-dimensional double spiral system by English scientist William Crookes in 1888.
Crookes added the newly-discovered noble gases (helium, neon, argon, krypton, xenon, radon) to his system, which helped persuade Mendeleev that his table could be adapted to accommodate them.
But more interestingly, Crookes’ periodic system illustrated his theory of the evolution of the elements. In this, elements formed in a plasma (a hot state of matter) inside stars. As temperatures cooled, they evolved from the lightest element, hydrogen, at the top of his spiral, to the heaviest, uranium, at the bottom.
Crookes' original model physically embodies one of the first evolutionary theories of the elements.
Is the famous periodic table the final one?
In the pursuit of the ultimate table, there were about 700 alternative versions published in the century after Mendeleev’s table of 1869.
Whatever their shape, from spirals and helices to zig-zags, circles and blobs, what unites them is the periodic law—that elements fall into repeating groups when ordered by their increasing atomic numbers.
But none of these has won the title of the definitive table.
Even the famous version you might know provokes fierce debate among chemists about where certain groups or elements, like hydrogen, should be placed. And as new elements are added, it will continue to evolve.
In recent decades, the Internet has opened up the practice of periodic table making to a wider public. As well as alternative forms, there are alternative contents: you can find periodic tables of almost anything, from wine to football.
This proliferation of periodic tables not only reflects the ongoing scientific endeavour to classify the world around us.
It also shows, as these tables have made the journey from textbook to tea mug design, how rooted science is in our cultural life.
Find out more about periodic tables
- Eric R. Scerri 'The Periodic Table: A Very Short Introduction' (OUP: 2011)
- Eric R. Scerri, The Periodic Table: Its Story and Its Significance (OUP: 2007)
- Edward G. Mazurs, Graphic Representations of the Periodic System during One Hundred Years (University of Alabama Press, 1974)
- Science Museum Blog, The periodic table in three dimensions
- Royal Society of Chemistry, Development of the periodic table
- Nature, Celebrate the women behind the periodic table
- New Scientist, Up and atom: The fights to put people into the periodic table
- BBC Bitesize, The most weird and wonderful elements in the periodic table