History of the Periodic Table

The Greeks were the first to float the idea that matter was composed of elements. Aristotle believed these elements to be Earth, Fire, Air and Water, whilst Democritus theorized an atomic theory of matter — that all matter was composed of indivisible units or “atomos.” (”Atomos” means indivisible). Antonie Lavoisier in the 1700s was the first to write an extensive list identifying 33 elements, and distinguishing between metals and non-metals, and John Dalton developed his atomic theory around the year 1800.

As far as sorting these elements into some form of table, Dmitri Mendeleev, though given full credit, was not the first (and not the last). In the 1820s, Jons Jakob Berzelius created a table of elements sorted by their atomic weights, and he replaced the Greek symbols for the elements with English abbreviations.

Johann Wolfgang Döbereiner noted that elements could be arranged into triads according to their physical properties, with the middle element of the triad exhibiting properties in-between the outer two elements. For example, he noted that the atomic weight of the middle element was the average of the atomic weights of the outer two elements. An example of such a triad is lithium, sodium and potassium, three of what we know call the “alkali metals.”

Stanislao Cannizaro determined atomic weights for the elements that were already known in the 1860s, and a table of these elements was arranged by Newlands, beginning with hydrogen. J.A.R. Newlands identified a “Law of Octaves,” in which “the eighth element, starting from a given one, is a kind of repetition of the first.”

Alexandre-Émile Béguyer de Chancourtois turned these atomic masses and repeating properties into a three-dimensional system on a cylinder, which he called the vis Tellurique. In this way,, the known elements were placed in unbroken order of increasing atomic mass.

In 1869, both Dmitri Mendeleev and Lothar Meyer developed periodic tables. The Russian Mendeleev was a chemistry teacher who arranged the periodic table according to increasing atomic mass. His greatest contribution was not the table itself, however, but his recognition of the periodicity of chemical properties, called The Periodic Law, which states that, “if all the elements be arranged in order of their atomic weights a periodic repetition of properties is obtained.” All the more so, Mendeleev’s Periodic Table left gaps for elements that had not yet been discovered, whose properties could be predicted by their placement within the table. When these elements were ultimately discovered, they fit neatly into those gaps, and matched the chemical properties predicted for them.

The Periodic Table has changed much since Mendeleev’s output, but the Periodic Law remains. Firstly, the Noble Gases had not been identified in Mendeleev’s time, so he could not predict their existence. Between the years of 1894 and 1898, Sir William Ramsay discovered five noble gases, and placed them in their own group on the right column of the Periodic Table.

Then, after Henry Moseley was able to identify the atomic numbers of elements using x-ray diffraction data, the Periodic Table of the Elements was reordered in terms of atomic number, not atomic mass.

When Glenn Seaborg discovered some heavier transuranium elements, he placed them at the bottom of our Modern Periodic Table, giving way to the Actinides series of the inner transition metals.