Lothar Meyer Atomic Curve

Lothar Meyer was also working on a periodic table. Although his work was published in 1864, and was done independently of Mendeleev, few historians regard him as an equal co-creator of the periodic table. For one thing, Meyer's table only included 28 elements. Furthermore, Meyer classified elements not by atomic weight, but by valence alone. Finally, Meyer never came to the idea of predicting new elements and correcting atomic weights. Only a few months after Mendeleev published his periodic table of all known elements (and predicted some new elements to complete the table, plus some corrected atomic weights), Meyer published a virtually identical table. While a few people consider Meyer and Mendeleev the co-creators of the periodic table, most agree that, by itself, Mendeleev's accurate prediction of the qualities of the undiscovered elements lands him the larger share of credit. In any case, at the time Mendeleev's predictions greatly impressed his contemporaries and were eventually found to be correct.

 Periodic table according to Lothar Meyer, 1870

John Newlands Law of Octaves

John Newlands was an English chemist who in 1865 classified the 56 elements that had been discovered at the time into eleven groups which were based on similar physical properties.

Newlands noted that many pairs of similar elements existed which differed by some multiple of eight in atomic number. However, his law of octaves, likening this periodicity of eights to the musical scale, was ridiculed by his contemporaries. It was not until the following century, with Gilbert N. Lewis' valence bond theory (1916) and Irving Langmuir's octet theory of chemical bonding (1919) that the importance of the periodicity of eight would be accepted.

Classifying Elements

By 1869, a total of 63 elements had been discovered. As the number of known elements grew, scientists began to recognize patterns in the way chemicals reacted and began to devise ways to classify the elements.

Dobereiner's Periodic Table

A German scientist called Johann Dobereiner put forward his law of triads in 1817. Each of Dobereiner's triads was a group of three elements. The appearance and reactions of the elements in a triad were similar to each other.

Atomic masses At this time, scientists had begun to find out the relative atomic masses of the elements. Dobereiner discovered that the relative atomic mass of the middle element in each triad was close to the average of the relative atomic masses of the other two elements. This gave other scientists a clue that relative atomic masses were important when arranging the elements.