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So what is the world made of? This is certainly something we had taken for granted, even though we experience it with our senses – what we eat, smell, touch and see.
Certainly with the advancement of chemistry throughout the ages, we have managed to create thing not found in nature, but how did we make sense of the nature of things so that we can manipulate them? |
"I saw in a dream a table where all elements fell into place as required. Awakening, I immediately wrote it down on a piece of paper, only in one place did a correction later seem necessary." - Dmitri Mendeleev, as quoted by Inostrantzev
Let’s assume you are a chemical engineer trying to create some new super-strong, superconductive miracle material; how do you start? Before you even consider the molecular structure of the material (which is important, but that’s a different topic), maybe you should take a look at its basic building blocks, that is, the elements that’s part of its structure, as well as their individual properties.
The hypothetical case just now is actually true, and it gave us graphene, a material consisting of a sheet of carbon atoms – an element known for its strength (think diamonds), and conductivity. And similarly, we can develop other miracle materials thanks to the periodic table, which allows us to predict the character and properties of elements that have yet to exist. How did we came to develop such a useful tool? Just as in all scientific endeavors, it began with an idea…
Back when what we know as science was in its infancy, there were the philosophers, who made up their lack of technology with pure reasoning. In ancient times Plato postulates that everything in the universe were made up of basic and ‘pure’ stuff. Through his observations it became the mainstream idea that these stuffs are fire, water, earth and air.
The hypothetical case just now is actually true, and it gave us graphene, a material consisting of a sheet of carbon atoms – an element known for its strength (think diamonds), and conductivity. And similarly, we can develop other miracle materials thanks to the periodic table, which allows us to predict the character and properties of elements that have yet to exist. How did we came to develop such a useful tool? Just as in all scientific endeavors, it began with an idea…
Back when what we know as science was in its infancy, there were the philosophers, who made up their lack of technology with pure reasoning. In ancient times Plato postulates that everything in the universe were made up of basic and ‘pure’ stuff. Through his observations it became the mainstream idea that these stuffs are fire, water, earth and air.
The Platonic elements and their properties
The Greek philosophers’ reasoning seems to make sense at the time. If we were to burn wood, it will combust into ash, smoke, heat and light, which corresponds to earth, air and fire. If we leave a piece of meat to decompose, it will disintegrate to air (the stink it gave off), water (from the blood) and earth (the decayed residue).
However, they also find out that certain things can’t be broken down, disintegrate or decomposed into these so-called four elements; materials such as gold, silver, lead and mercury. Due to their ‘purity’, these items were given mystical attributes, are thought to contain vital factors that may prolong life. Chinese Taoist alchemists for example have been using gold, mercury and sulphur in the attempts to make elixirs of life at the behest of emperors.
As we moved from the ancient times to the age of reason, systematic questions on what makes an element, an element. The Platonic element of ‘air’ have been broken down into other components by Henry Cavendish and Antoine Lavoisier; William Nicholson and Anthony Carlisle used electrolysis to disintegrate ‘water’; and the refining of various ores into metallic elements also has shown that ‘earths’ are not the basic building blocks of nature.
It wasn’t until the 19th century, after quite a number of new elements were discovered that people began to notice that some of them share certain properties. For instance lithium and sodium reacts violently with water, chlorine and bromine are more volatile with metals than non-metals. The first attempts to rationalize this was by Johann Dobereiner, a German chemist, who grouped similarly reactive elements into group threes and noticed that if they were ordered by atomic weight, the middle element would have the weight that’s roughly equal to the average of the sum of the other two.
Unknowingly, Dobereiner had discovered the periodic law, whereby elements tend to have similar characteristics at regular intervals when ordered by their atomic weights. This simple, but significant, innovation was first codified by Alexandre-Emile Chancourtois, a French geologist, though it may be due to his ‘outsider’ status (i.e. not being a chemist) that his views were largely ignored.
However, they also find out that certain things can’t be broken down, disintegrate or decomposed into these so-called four elements; materials such as gold, silver, lead and mercury. Due to their ‘purity’, these items were given mystical attributes, are thought to contain vital factors that may prolong life. Chinese Taoist alchemists for example have been using gold, mercury and sulphur in the attempts to make elixirs of life at the behest of emperors.
As we moved from the ancient times to the age of reason, systematic questions on what makes an element, an element. The Platonic element of ‘air’ have been broken down into other components by Henry Cavendish and Antoine Lavoisier; William Nicholson and Anthony Carlisle used electrolysis to disintegrate ‘water’; and the refining of various ores into metallic elements also has shown that ‘earths’ are not the basic building blocks of nature.
It wasn’t until the 19th century, after quite a number of new elements were discovered that people began to notice that some of them share certain properties. For instance lithium and sodium reacts violently with water, chlorine and bromine are more volatile with metals than non-metals. The first attempts to rationalize this was by Johann Dobereiner, a German chemist, who grouped similarly reactive elements into group threes and noticed that if they were ordered by atomic weight, the middle element would have the weight that’s roughly equal to the average of the sum of the other two.
Unknowingly, Dobereiner had discovered the periodic law, whereby elements tend to have similar characteristics at regular intervals when ordered by their atomic weights. This simple, but significant, innovation was first codified by Alexandre-Emile Chancourtois, a French geologist, though it may be due to his ‘outsider’ status (i.e. not being a chemist) that his views were largely ignored.
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The Mendeleev Breakthrough
Although the notion of elemental periods have been noticed by various chemists, somehow the idea of tabulating it didn’t quite catch on until the 19th century. By that time, thanks mainly to the discovery of many new elements, the pattern that Dobereiner and Chancourtois envisages became more and more apparent. But the rationalization of these patterns were not discovered in Germany nor France, but in Russia. By the second half of the 19th century, Dmitri Mendeleev, a largely unknown Russian chemist, was amongst those who took notice of these periodical frequencies. He would play a game of chemical ‘solitaire’ whereby matching all the known elements at the time with their respective properties – what compounds do they react with? Whether they are metals or not? Do they respond similarly with acids and alkalines? It’s more than a puzzle, it’s an obsession. Then, on a cold February night in 1869, he had a dream. A table was brought to him, where the elements – one after another – fell into its respective places, the periodic table. |
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Mendeleev's periodic table
Whether it actually happened is of little consequence, what it had resulted is the systematic structuring of all known elements into a simple, and understandable matrix of homologues. This leads to another advantage of the periodic table: predictability. When Mendeleev had published his work, only around 60 were identified and had their properties known. Foreseeing that science may have yet to discover more, he had gaps left on it for those that are, for all intents and purposes, hypothetical. If we can add more to his achievements, Mendeleev can be said to be a co-discoverer of gallium (of which he tentatively called eka-aluminium), germanium (eka-silicon), and dubnium (eka-tantalum). And not merely their existence, but their properties as well, making the tedious job of handling such delicate (and yet unknown) specimens safer and easier.
It would only take only a few years for his colleagues to fill in the blanks Mendeleev had left, and as science marches on, the table was amended to include the noble gasses, and as the nuclear age came into being, the actinides and lanthanides, thus sealing his legacy among the greats. He may have left it incomplete, but it is significant that he converted the unknown unknowns to known unknowns, like a map to a lost wanderer.
It would only take only a few years for his colleagues to fill in the blanks Mendeleev had left, and as science marches on, the table was amended to include the noble gasses, and as the nuclear age came into being, the actinides and lanthanides, thus sealing his legacy among the greats. He may have left it incomplete, but it is significant that he converted the unknown unknowns to known unknowns, like a map to a lost wanderer.
Ponder this
Why is it radon, having the atomic weight of 86, is a gas while boron, with an atomic weight of 5, is solid?
Why is hydrogen in Group 1?
Are there an infinite number of possible elements? Or is there an upper limit of how big a nucleus can get?
Discuss
What are the reasons for this periodic pattern? And what is its relation with the elements' atomic weight? Are there patterns of periodicity when they are listed in any other manner?
Further readings
The development of the periodic table, by the Royal Society of Chemistry. An excellent summarisation on the history and formulation of the periodic table.
The periodic table, by MIT OpenCourseWare. An excellent, comprehensive video on the periodic table.
Dynamic periodic table, an interactive table to tinker with.
Dmitri Mendeleev, from Wikipedia. Know the man behind the discovery.
