History of the periodic table

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Julius Lothar Meyer

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Dmitri Mendeleev

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  • Created on: 28-04-10 08:52
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Classifying Elements
Julius Lothar Meyer
Meyer is best known for the share he had in the periodic classification
of the elements. He noted, as did J. A. R. Newlands in England, that
if they are arranged in the order of their atomic weights they fall into
groups in which similar chemical and physical properties are repeated
at periodic intervals and in particular he showed that if the atomic
weights are plotted as ordinates and the atomic volumes as abscissa,
the curve obtained presents a series of maxima and minima, the most
electropositive elements appearing at the peaks of the curve in the
order of their atomic weights.
Mendeleev published his periodic table of all known elements (and predicted several new
elements to complete the table, plus some corrected atomic weights) in 1870. Working
completely independently, a few months later, Meyer published a revised and expanded
version of his 1864 table, virtually identical to that published by Mendeleev, and a paper
showing graphically the periodicity of the elements as a function of atomic weight.
Dmitri Mendeleev
He is credited as being the creator of the first version
of the periodic table of elements. Using the table, he
predicted the properties of elements yet to be
discovered.
He stated
1. The elements, if arranged according to their
atomic weight, exhibit an apparent periodicity
of properties.
2. Elements which are similar in regards to their
chemical properties have atomic weights
which are either of nearly the same value
(e.g., Pt, Ir, Os) or which increase regularly
(e.g., K, Rb, Cs).
3. The arrangement of the elements in groups of elements in the order of their atomic
weights corresponds to their socalled valences, as well as, to some extent, to their
distinctive chemical properties as is apparent among other series in that of Li, Be,
B, C, N, O, and F.
4. The elements which are the most widely diffused have small atomic weights.
5. The magnitude of the atomic weight determines the character of the element, just as
the magnitude of the molecule determines the character of a compound body.
6. We must expect the discovery of many yet unknown elements­for example, two
elements, analogous to aluminum and silicon, whose atomic weights would be
between 65 and 75.
7. The atomic weight of an element may sometimes be amended by knowledge of
those of its contiguous elements. Thus the atomic weight of tellurium must lie

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Here Mendeleev was wrong as the
atomic mass of tellurium (127.6) remains higher than that of iodine (126.9).
8. Certain characteristic properties of elements can be foretold from their atomic
weights.…read more

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