Think back to your days in chemistry. What tools were most useful to you? Your goggles? A lab coat? Maybe it was the notebook where you scribbled furiously so as not to forget anything. However, there’s another tool you might have forgotten, that has proven itself extremely useful for generations of students and scientists: the periodic table of elements.
A periodic table consists of a neatly arranged table with color-coordinated rows and columns of elements (a substance whose atoms have the same number of protons), all with one- or two-letter designations, and some numbers representing chemical properties scribbled in each square. One of the most significant achievements in science, the periodic table, can be found everywhere, from escape rooms to shower curtains, to mugs and classrooms all over the world. The periodic table represents a common language that chemists, in addition to people of various scientific or non-scientific backgrounds, can decipher. This year marks the 150th anniversary of the periodic table, and it’s largely attributed to one brilliant mind, Dmitri Mendeleev.
Growing up on the outskirts in a small town called Tobolskin, Siberia (born in 1834), Dmitri Mendeleev faced many hardships early in his life, including the untimely death of his father and a workplace fire at his mother’s family’s glass factory. After moving to St. Petersburg with his brother and mother, Mendeleev was accepted into the University of St. Petersburg, where he went on to successfully defend his master’s thesis in 1856 on the relationships between volumes of substances and their crystallographic and chemical properties. Mendeleev received two years of state funding to study abroad, and as such, found himself at Heidelberg University in Germany. There, he conducted research on topics ranging from evaporation and surface tension to intermolecular forces, which are the forces that mediate interactions between molecules. Upon returning to St. Petersburg, he resumed his teaching duties and had a productive career publishing scientific research articles and an organic chemistry textbook. It was not until the university appointed him professor of general chemistry (and when he started writing an inorganic chemistry textbook) that his focus shifted to the idea of an orderly arrangement of the chemical elements, according to their properties.
Birth of the Periodic Law
Unhappy with the current Russian textbook on inorganic chemistry, Mendeleev set out to write his own version. The result of his determination was the Osnovy khimii or The Principles of Chemistry (curious readers can find one on display at the Rare Book & Special Collections Library at the University of Illinois at Urbana-Champaign). While he was writing one of the chapters, he identified a pattern where “The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.” After further side-by-side comparisons, Mendeleev realized that the elements could be organized by their atomic weights. Each element has its own atomic weight, distinct from all other elements. These weights are made up of subatomic particles that encompass that specific element. Mendeleev noted that some elements with almost equal atomic weights shared common properties with one another. By using the atomic weights to write all 63 known elements on individual note cards and arranging them like a game of solitaire, Mendeleev arrived at his table of elements. His discovery became known as the Periodic Law, which states that similar properties recur periodically when elements are arranged according to increasing atomic weight. As shown in Mendeleev’s original, handwritten periodic table, the elements were organized by similar characteristics (horizontal rows) and increasing atomic weight (vertical columns). Mendeleev went on to conclude “the size of the atomic weight determines the nature of the elements.” Excited with his discovery, Mendeleev hastily sent his table to the printer for his textbook and for presentation to the Russian Chemical Society. Much to his chagrin, however, other chemists showed little interest in his formulated law when his colleague, Professor Nikolai Menschutkin, presented his periodic table (Mendeleev was ill) to the Russian physico-chemical society in March of 1869. Even though his first presentation was not well received, Mendeleev refused to give up on his discovery. He continued working and went on to predict the locations of elements within the periodic table that had not yet been discovered. It was not until the discovery of correctly predicted elements gallium, scandium, and germanium in 1875, 1879, and 1886, respectively, that Mendeleev’s law became widely accepted by the chemistry community.
In the coming years, Mendeleev received many awards and international recognition, including his nomination for the Nobel Prize in 1906. Although he succumbed to influenza in 1907, his stamp on the chemistry world became iconic when a new element (#101) was born and fittingly named “Mendelevium” in 1955. What better way to immortalize such a groundbreaking discovery than to have an element with your namesake in the icon you discovered?
As 2019 marks the 150th birthday of the periodic table, Mendeleev’s contribution to not only chemistry but also science as a whole is remembered. For those interested in attending or creating events celebrating Mendeleev’s achievement, a list of activities and information on creating events can be found here (make sure to use #IYPT2019).
Alisa King is a doctoral candidate in the department of microbiology at the University of Illinois at Urbana-Champaign. When she’s not conducting research or playing video/board games, she’s dipping her toes in science writing (and trying to finish her fantasy book). Twitter: @AlisaM_K.