John Newlands and the law of octaves
The law of octaves was John Newlands’ 1865 observation that when the elements are listed in order of atomic weight, every eighth element has properties similar to the first, like the eighth note of a musical scale. It was dismissed at first, but it was an important step toward the periodic table, and in 1887 the Royal Society honored Newlands with its Davy Medal.
Who was John Newlands?
John Alexander Reina Newlands (1837–1898) was born in London and studied at the Royal College of Chemistry. His mother was of Italian descent, and in 1860 he went to Italy to fight as a volunteer with Giuseppe Garibaldi’s forces in the campaign to unify the country. Back in London he worked as an analytical chemist and later as a chemist in the sugar refining industry.
Every eighth element
In a series of short papers in the journal Chemical News beginning in 1864, Newlands arranged the known elements in order of increasing atomic weight and gave each one a position number. In August 1865 he pointed out that elements with similar properties tended to appear seven places apart. Lithium was number 2, sodium 9 and potassium 16; the same spacing linked fluorine and chlorine, and magnesium and calcium. Because each eighth element echoed the first, he compared the pattern to an octave in music and called it the law of octaves.
We now know why the count came out at eight. The noble gases had not yet been discovered, so each run of light elements had seven members, and the eighth element started the next run.
A cool reception
On March 1, 1866, Newlands presented his ideas to the Chemical Society in London. The audience was unconvinced. One member, the physicist George Carey Foster, asked whether Newlands had ever tried listing the elements in alphabetical order, suggesting that almost any arrangement would throw up occasional coincidences. The society declined to publish the paper, explaining that it did not print purely theoretical work.
Where the octaves went wrong
The critics had real grounds for doubt. The pattern held up well for the light elements, as far as calcium, but beyond that it fell apart: iron landed in the same line as oxygen and sulfur, and cobalt and nickel had to share a single place in the family of fluorine and chlorine. In several spots Newlands squeezed two elements into one position, and his table left no empty spaces for elements still to be discovered. When the next new element turned up, there was nowhere for it to go.
Recognition at last
After Mendeleev’s periodic table of 1869 won acceptance, Newlands argued that he had spotted the periodic pattern first, and in 1884 he gathered his papers into a book to make his case. The Royal Society, which had given its Davy Medal jointly to Mendeleev and Lothar Meyer in 1882, awarded the same medal to Newlands in 1887 for his discovery of the periodic law.
Newlands is now remembered as one of the most important forerunners of the periodic table. His idea of giving each element a numbered place in a sequence took on new meaning in 1913, when Henry Moseley showed that every element has its own atomic number.