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 Tables
Monday, 10 September 2012
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.
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.
Dobereiner's Periodic Table
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.
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