Dobereiner's work focused on the relationships among the elements in a triad but gave no hint of any relationships between triads. The next major step toward determining the patterns in the chemistry of the elements was taken by John Newlands in 1865. Newlands found that when he listed the elements in order of increasing atomic weight, they seemed to fall into seven families that contained elements with similar chemical properties. His table listed these families in horizontal rows, as shown in Table 7.2.
Newlands was the first to recognize that the elements fall into a pattern in which their properties repeat at regular intervals when they are listed in order of increasing atomic weight. He was also the first to assign atomic numbers to the elements. Unfortunately, his work was not accepted by his peers, and the paper in which he described his table was rejected by the Journal of the Chemical Society.
In retrospect there are obvious problems with Newlands' table of the elements. The first row, for example, groups elements with similar chemical properties (such as F, Cl, Br, and I), but it also includes elements that have totally different chemical properties (such as Co, Ni, Pd, Pt, and Ir). Furthermore, at a time when elements were being discovered with some regularity, Newlands failed to leave room in his table for new elements.
These mistakes might have resulted from Newlands' attempt to link the periodicity of the elements with that which occurs in music. Newlands saw a pattern in which intervals of seven elements often separated elements with similar chemical properties. There were seven elements between fluorine and chlorine, for example, and seven between sodium and potassium. This reminded him of a musical scale, in which one note in a key is separated from its octave by an interval of seven notes. Newlands was so enthralled with this "law of octaves" that he made the mistake of trying to force the elements into this pattern.
|History of Chemistry|