In the mid-19th century, chemistry was a rapidly evolving field, with many elements being discovered. This highlighted a challenge: organizing elements and understanding their relationships. Scientists sought a framework to bring order to chemical knowledge, identifying patterns and periodic behaviors. Julius Lothar Meyer, a German chemist, contributed significantly to the periodic system’s development.
Meyer’s Early Insights into Periodicity
Meyer’s investigations into element properties laid foundational groundwork for understanding periodicity. He focused on physical properties, particularly the relationship between atomic volume and atomic weight. Meyer defined atomic volume as the quotient of an element’s atomic weight and its specific gravity, quantifying the space occupied by atoms.
A significant contribution was his “atomic volume curve,” published in 1870. In this graph, he plotted atomic volume against atomic weight. The curve displayed a wave-like pattern, revealing a periodic rise and fall in atomic volumes.
Alkali metals like sodium, potassium, and rubidium appeared at the peaks, indicating larger atomic volumes, while transition metals occupied the troughs. This visual evidence suggested elements with similar properties recurred at regular intervals, providing graphical proof of the periodic law.
The Development of Meyer’s Periodic System
Meyer also created periodic tables. His 1864 textbook, “Die modernen Theorien der Chemie,” included an early table classifying 28 elements. This grouped elements into six families based on their valence, a measure of an atom’s combining power. This showed his early recognition of valence as an organizing principle alongside atomic weight.
Meyer developed a more comprehensive table in 1868, though it was not published until 1870. This arrangement relied on increasing atomic weight, incorporating valence and observed periodicity of physical properties. His graphical display of atomic volume periodicity offered a visual argument for periodic relationships among elements.
Shared Discoveries and Scientific Recognition
Lothar Meyer and Dmitri Mendeleev independently developed similar periodic systems concurrently. Meyer emphasized physical properties, like his atomic volume curve, providing evidence for periodicity. Mendeleev, also using atomic weight, focused more on chemical properties and predicting undiscovered elements.
Mendeleev published his table in 1869, a year before Meyer’s 1870 table. Mendeleev’s earlier publication and successful predictions for elements like gallium, scandium, and germanium contributed to his greater historical credit.
Meyer made predictions but was more cautious and did not emphasize this aspect as much. Mendeleev was more assertive in defending his periodic law and adjusting atomic weights.
Despite differing recognition, both received the Davy Medal in 1882, acknowledging their contributions to element classification.