English chemist John Newlands was one of the first to propose a comprehensive system for classifying the approximately 62 known elements in 1864. At the time, chemists primarily used atomic weight as the basis for arrangement, and Newlands adopted this approach. Newlands’ primary contribution was the discovery that arranging elements by increasing atomic weight revealed a pattern of recurring chemical properties.
The Concept of the Law of Octaves
Newlands observed that when elements were arranged in a continuous series based on increasing atomic weights, the chemical and physical properties of the first element were repeated by the eighth element in the sequence. This pattern led him to formulate the “Law of Octaves,” which drew an analogy to the musical scale where the eighth note repeats the first. The elements were grouped into rows of seven, with the eighth element starting the next row and falling directly beneath the first element with which it shared similar characteristics.
For instance, starting with Lithium (Li), the eighth element was Sodium (Na), and the eighth element after Sodium was Potassium (K). All three of these elements exhibit similar chemical behaviors, such as reacting vigorously with water. The sequence was arranged in seven columns, or “families,” with the elements in each column displaying similar properties. The Law of Octaves successfully highlighted the periodic nature of elemental properties for the lighter elements.
Flaws in Newlands’ Arrangement
The Law of Octaves only held true for the first 16 or so elements. Specifically, the periodic repetition of properties was reliable only up to the element Calcium (Ca). Beyond Calcium, the pattern broke down, and the properties of the eighth element no longer consistently resembled the first.
To force the heavier elements into his seven-column structure, Newlands had to make several arbitrary adjustments. He was sometimes compelled to place two elements, such as Cobalt (Co) and Nickel (Ni), into the same position within a column. Furthermore, he grouped elements with vastly different chemical properties together; for example, Cobalt and Nickel were placed in the same column as halogens like Fluorine and Chlorine. These forced placements were a major point of criticism because they prioritized the “eighth element” rule over chemical similarity.
Newlands also faced ridicule from the scientific community for his analogy to music. His table failed to leave any gaps for elements that had not yet been discovered, as he mistakenly predicted that only 56 elements would be found in nature. When new elements were discovered, they could not be logically incorporated into his existing arrangement.
Establishing the Principle of Periodicity
Despite the Law of Octaves’ limitations, Newlands’ most enduring contribution was his clear articulation of the concept of periodicity in chemical properties. He explicitly suggested that the chemical properties of elements repeat at regular intervals when they are ordered by atomic weight. This principle—that element properties are a periodic function of their atomic mass—became the fundamental basis for all subsequent successful attempts at element classification.
Newlands’ work served as a crucial intellectual precursor for later chemists, most notably Dmitri Mendeleev and Lothar Meyer, who refined the concept into the Periodic Law. Although Mendeleev is often credited with the comprehensive periodic table, Newlands was the pioneer who first connected the idea of a systematic arrangement with the recurring nature of element properties. Although initially rejected for publication by the Chemical Society, Newlands’ foundational insight was eventually recognized, and he was awarded the Davy Medal by the Royal Society in 1887 for his discovery of the periodic law.