The lower figures show his calculations of the differences between the atomic weights of sodium and lithium (23 – 14* = 9), potassium and magnesium (39 – 24 = 15), rubidium and zinc (85 – 56 = 20), cesium and cadmium (133 – 112 = 21). Mendeleev’s sketched notes on the back on the invitation to visit a local cheese co-operative. Before arriving at any new ordering principle he started volume 2 by discussing another well-known group of elements, the alkali metals that include lithium, sodium and potassium.įigure 1. On moving on to the second volume he realized that he needed an organizing principle for all the remaining elements. He ended the book with the halogens, including chlorine, bromine and iodine. While in the process of writing his textbook, The Principles of Chemistry, Mendeleev completed the book by dealing with only eight of the then known sixty-three elements. The usual version of how Mendeleev arrived at his discovery goes something like this.

This in turn meant that I had to thoroughly review the literature on this particular historical episode, which will form the basis of this blog.

It was very gratifying to see how keen the film-makers were on understanding precisely how Mendeleev arrived at his famous first periodic table of 1869. I just returned home from being interviewed for a new public television program on the mystery of matter and the search for the elements.

Periodic table elements explained