This year marks the 150th anniversary of the discovery, or invention, of the periodic table of the elements, one of the most important, if least dramatic, of all scientific breakthroughs. Chemistry has a bad reputation among non-chemists, perhaps because it is the first place in science where a schoolchild comes up against the stubborn complexity of nature. The organising principles of physics appear simple; evolution makes biology appear a well-ordered process, at least until it’s examined in detail. But chemistry is awkward and lumpy. There are endless facts to memorise, and there are few obvious and intuitively pleasing answers to questions such as why the periodic table has eight columns and not seven or nine. There is not even a hero figure like Darwin, Newton or Einstein whose story can dramatise our understanding of the subject. If there were, it would be Dmitri Mendeleev, the Russian who first organised the known elements into an arrangement which not only fitted them together but had predictive value: it suggested new elements that might be discovered, and what their qualities would be.

This was not a complete theoretical understanding, but it exposed the phenomena which a theory must explain. In some sense the elements had been known since gold was first washed out of gravel, long before writing was invented. But the existence of some simple and apparently irreducible kinds of stuff did not prove and might not even imply that every substance in the world was made from simpler elements combined. The idea that water is really the combination of two gases, themselves never found in a pure state in nature, seems entirely fanciful until it is proved by experiment. In the 18th century, following Antoine Lavoisier, chemists began to isolate more and more elements from the apparent chaos around them. But their qualities and modes of reaction formed no discernible pattern. The discovery of this pattern and the development of its implications was Mendeleev’s great contribution.

The periodic table made possible the modern industrial world. It didn’t just break down the world into its constituents; it supplied the knowledge needed to recombine these elements in new ways, from fertiliser to poison gas, from medicines to plastic. One of the remarkable things about this is that it worked even without a proper theoretical foundation. Not until 1913, when the British scientist Henry Moseley fired x-rays, then newly discovered, at elements and measured what came off, was it apparent how the underlying structure of atoms produced the qualities we detect in the elements.

X-rays were only the start of the merger of chemistry with physics. At the extreme edge of present-day science lies the creation of new elements that can only be produced artificially: the most recent, oganesson, has only been observed as six short-lived atoms. But long before then, chemical analysis and understanding had been turned inwards, on to the bodies of living things. These techniques, widely available, make it possible to understand all the processes of life as interlocking reactions which can be tweaked to our advantage.

One effect of this is that chemistry as a distinct subject tends to disappear. At the simplest level, it merges with physics; at its most complex it becomes a tool of biology. In both cases, chemistry, like all other science, is increasingly conducted inside computer simulations. But the depth and subtlety of the periodic table stands as one of the most remarkable feats of the human intellect.