Celebrating Mendeleev

John Harrison

This year is the 150th anniversary of the first publication of Dmitry Mendeleev’s Periodic Table of Chemical Elements. Mendeleev certainly hit the jackpot in the fame charts, every single person who has studied chemistry, or anything remotely connected with chemistry, regardless of where they are born and educated, has to know something about the elements and the periodic table, and have come across his name. The United Nations, no less, has proclaimed 2019 to be the ‘International Year of the Periodic Table of Chemical Elements’.

No one has bothered to ask the question: ‘was Mendeleev the first to come up with a periodic table of chemical elements?’ Some chemists think not. This is a fair enough assumption, because many of the world’s great inventions have been worked on and even invented simultaneously by like-minded individuals around the planet. In some cases, the individuals had no idea of the existence of each other. The concept of ‘multiple independent discovery’ or ‘simultaneous invention’ is well known and those who believe in destiny could cite examples of simultaneous but independent inventions as proof of fate, or providence, others would point to the existence of similar scientific and societal factors to explain such phenomena.

To mention but a few instances of this mind boggling idea, we can refer to the C17 independent formulation of calculus by Isaac Newton, Gottfried Wilhelm Leibniz and others, the crossbow (invented independently in China, Greece, Africa, northern Canada, and the Baltic countries), and magnetism (discovered independently in Greece, China, and India).

John Dalton
’s second list of elements was published in the first volume of a work in 1808.  This work included twenty elements, with their [often incorrect] atomic masses (above) and some combinations of the elements (below).

The periodic table, however, was not invented simultaneously by independent scientists. It seems to have evolved from the 1780s onwards, one scientist picking up where the other left off. That is according to scientists at St. Catharine’s College, Cambridge, where an exhibition is to be held in April about periodic tables. The first list of elements emerged around the time of the French Revolution in the late 1780s, and the first list of atomic masses was drawn up by Manchester chemist John Dalton roughly two decades later. This is what chemists from St. Catharine’s College have written on the subject in their university online magazine:

‘…No less than six different chemists from around the world each came up with their own versions of the iconic table in the 1860s. The first person to arrange all the then-known elements by mass and then look for the repeating properties of related elements was the French mineralogist Alexandre-Émile Béguyer de Chancourtois in 1862.  Béguyer plotted his elements around a cylinder or helix with a circumference of sixteen atomic mass units and found elements with similar properties aligned in vertical groups down the cylinder. This coloured chart, over 1.5 metres in length, was published in very limited numbers and is now incredibly rare. In addition to Mendeleev’s first published versions of his table, including one signed by the great chemist himself, earlier forms created by two British chemists are also featured.’

Mendeleev published his periodic table in 1869

Mendeleev published his table in 1869, and to give the man due credit, he appears to have assimilated, not ‘copy and pasted’ knowledge from all known previous versions. His work was designed to illustrate periodic trends of then-identifiable elements. He also predicted some properties of unidentified elements that were expected to fill gaps within the table. Most of his forecasts have proved to be correct. Mendeleev’s idea has been slowly expanded and refined with the discovery or synthesis of further new elements and the development of new theoretical models to explain chemical behaviour. In other words, Mendeleev was the genius who was able to appreciate the depth of field of the subject and leave gaps, to be filled by others later for where he thought there should be corresponding elements. Hats off to Mendeleev, whose work has to be seen in perspective.