The periodic table of chemical elements (abbreviated periodic table) is well known to anyone who has ever entered into the scientific laboratory or classroom. The table itself is unrivaled in its ability to systematize and rationalize known chemical facts and to predict new elements. Russian chemist Dmitri Mendeleev holds the credit for its invention, although there were some other chemists before him working on the subject.
Before Mendeleev came onto the scene, there were a number of other scientists who paved the way:
The first table of simple chemical substances was proposed by the French chemist Antoine-Laurent Lavoisier in the book “Traité de Chimie Élémentaire" (1789). His table contained 33 elements divided into four groups: gases, non-metals, metals and soil.
In 1803, English chemist John Dalton proposed the principles of atomic theory, suggesting that all elements are composed of tiny, indestructible particles called atoms, which are all equal and have the same mass. Dalton assumed that hydrogen is the lightest element, so he introduced the concept of relative atomic mass (Ar), defined as the ratio of the mass of atom of the element and the mass of hydrogen atom.
Today’s system of chemical symbols, which is based on the initial letter (and where one more letter can be additionally added) of the Latin name of the element, was introduced in 1813 by the Swedish chemist Jons Jacob Berzelius.
Russian chemist Dmitri Mendeleev became the chemistry professor at the University of St. Petersburg in 1867. As he did not find a textbook that would satisfy his needs, he began writing his own. The result of his writings was a textbook named Principles of Chemistry. While writing the Principles, Mendeleev examined the relationships between the properties of elements in order to make a system that would classify them. The whole structure of the book depended on fundamental principles on how the elements could be ranked (63 different chemical elements were known then).
Mendeleev linked the problem with his favorite card game – solitaire. He wrote the names of the elements on the blank cards, adding their atomic mass and chemical properties. He hoped the elements would sort similar to cards; as groups with similar properties (such as colors of cards). Within each group, the elements would be ranked according to their atomic weight (emulating the numerical range of the playing cards). The resulting table, entitled “Proposal of the Elements,” was first presented to the Russian Chemical Society on March 1st, 1869.
Two years later, in 1871, Mendeleev brought out a new periodic table. He suggested that it was possible to predict properties of undiscovered elements for three new elements (ekaaluminum, ekaboron and ekasilicon). The scientific world was confused, and many mocked Mendeleev’s predictions.
Support for Mendeleev’s Predictions
In 1875, French chemist Paul Lecoq de Boisbaudran discovered a new element in the sample of zinc sulphide. The properties of the newly discovered element (called gallium from the Latin name for France) amazingly resembled ekaaluminum. In 1879, Swedish chemist Lars Fredrik Nilson discovered scandium with properties that Mendeleev predicted for ekaboron. Finally, in 1886, German chemist Clemens Winkler discovered a new element germanium, whose properties corresponded to those predicted by Mendeleev for ekasilicon.
These findings, proof of his predictions and evidence of its laws, put Mendeleev at the top of the contemporary scientific world; and for his achievements, he was awarded by the English Royal Society with the Meyer-Davy medal in 1882.
N.N. Greenwood, A. Earnshaw: Chemistry of the Elements, Butterworth-Heinemann, Oxford, 2001.
P. Strathern: Mandeleyev’s Dream: The Quest for the Elements, Thomas Dune Books, New York, 2000.
J. Emsley: The Elements: Oxford University Press, New York, 2000.
Mendeleev’s First Periodic Table – https://web.lemoyne.edu/~giunta/ea/mendeleevann.html
Photo of the Periodic Table of Elements via Wikimedia Commons
Photo of Dmitri Mendeleev by -.Serge Lachinov at ru.wikipedia [Public domain], from Wikimedia Commons