The Marvelous Prediction - The Birth of the Mendeleev Periodic Table (Part 1)

Dmitri Ivanovich Mendeleev

Dmitri Ivanovich Mendeleev (1834 – 1907) was a renowned chemist and social activist from Russia. He graduated from university at the age of 21 and worked as a high school teacher before moving on to teach chemistry at St. Petersburg University. Mendeleev traveled to France and Germany to further his studies and research. His greatest contribution was the development of the periodic table, a groundbreaking achievement that significantly advanced the field of chemistry, leading later generations to honor him as the “god of the door of Russian science.”

Mendeleev’s most remarkable contribution was the discovery of the periodic law governing the transformation of chemical elements, commonly known as the periodic law of elements.

When Mendeleev wrote “The Principles of Chemistry,” he considered the 63 discovered elements of the time and believed that there must be unified patterns among them, as all things are interconnected. To uncover this pattern, he registered these 63 elements on 63 cards, writing the name, atomic weight, and chemical properties of each element on the cards. He then shuffled these cards on his desk. One day, he suddenly realized that if the elements were arranged according to their atomic weights, a fascinating continuous transformation would emerge, resembling a marvelous piece of music. Mendeleev couldn’t hide his joy; he firmly believed that this pattern demonstrated the inevitable relationships among all things in the world and their cyclical nature.

Mendeleev felt as if he had found the key to the maze, uncovering the secrets of the entire palace. He arranged the elements into a periodic table, leaving some spaces empty for undiscovered elements. He published his work and patiently awaited confirmation of his periodic law from scientists around the world, but for four years, no new elements were discovered.

In 1875, the Paris Academy of Sciences received a letter from a scientist claiming he had created a new element from zinc ore, which he named “Gallium“. The properties of Gallium were similar to aluminum, with an atomic weight of 59.72 and a density of 4.7. Upon hearing this news, Mendeleev’s eyes lit up. According to his previous findings, this new element belonged to the “aluminum group,” something he had predicted four years earlier. However, he felt uneasy because, according to his periodic table calculations, the atomic weight of aluminum should be around 68, and its density should be between 5.9 and 6.0. Mendeleev believed he was correct and immediately wrote to the Paris Academy of Sciences to express his views.

The letter reached the scientist who had announced the discovery of Gallium. He was astonished that Mendeleev, without having seen Gallium, could confidently state its atomic weight and density, as if it were a joke. However, out of caution, the scientist re-evaluated the measurements, and the results remained unchanged.

Some time later, the French scientist received another letter from Mendeleev, filled with confidence. It seemed he was not merely discussing a new element but was posing a mathematical equation: “4 + ( ) = 10”. As a scientist, he could not dismiss Mendeleev’s insights. He re-examined Gallium and confirmed its properties, which astonished him as they matched Mendeleev’s predictions: the density of Gallium was indeed 5.94, an extraordinary coincidence.

Once this remarkable prediction was validated, the entire chemistry community was astounded. The theory of the periodic law of elements, which had been neglected for years, regained its significance. Many scientists sincerely congratulated Mendeleev on his brilliant discovery. The periodic table was quickly translated into multiple languages and disseminated worldwide. The periodic table of chemical elements (also known as Mendeleev’s periodic table) has served as a key for the discovery of numerous new chemical elements over the past century.

Four years later, Sweden discovered another new element, which some referred to as “Scandium.” As researchers delved deeper, they found that Scandium was indeed the element Mendeleev had predicted to be in the “group of Boron.” It became evident that the theory of the periodic law of elements could not only predict the positions of undiscovered elements but also their significant properties.

Mendeleev’s “The Principles of Chemistry” has been highly regarded and recognized as a classic textbook worldwide. One assessment of Mendeleev states: “In the history of chemistry, he has used a simple theme to evoke the entire world.”