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The following is an excerpt from a paper presented by Professor Mendeléeff in the Theatre of the Royal Institution, on Tuesday, June 4th, 1889. (reference)
It was in March, 1869, that I ventured to lay before the then youthful Russian Chemical Society the ideas upon the same subject, which I had expressed in my just written "Principles of Chemistry."Without entering into details, I will give the conclusions I then arrived at, in the very words I used:
The elements,
if arranged according to their atomic weights, exhibit an evident periodicity
of properties.
Elements
which are similar as regards their chemical properties have atomic weights which
are either of nearly the same value (e.g., platinum, iridium, osmium) or which
increase regularly (e.g., potassium, rubidium, cesium).
The arrangement
of the elements, or of groups of elements in the order of their atomic weights
corresponds to their so-called valences as
well as, to some extent, to their distinctive chemical properties, as is apparent
among other series in that of lithium, beryllium, barium, carbon, nitrogen,
oxygen and iron [sic. The printed speech in J. Chem.
Soc. says barium and iron. Obviously boron (B) and
fluorine (F) are meant. Mendeleev
The elements
which are the most widely diffused have small atomic weights.
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.
We must expect
the discovery of many yet unknown elements, for example, elements analogous
to aluminum and silicon, whose atomic weight would be between
65 and 75.
The atomic weight of an element may sometimes be amended by a knowledge
of those of the contiguous elements. Thus, the atomic weight of tellurium must
lie between 123 and 126, and cannot be 128.
Certain characteristic properties of the elements can be foretold
from their atomic weights.
Mendeleev rewrote each edition of Principles of Chemistry, including all new scientific data-particularly confirmations of the periodic law-and reanalyzing difficulties that had arisen to hinder its confirmation (inert gases, radioactivity, radioactive and rare-earth elements)"
The Periodic Law of the Chemical Elements Journal of the Chemical Society, 55, 634-56 (1889) By Professor Mendeléeff (Faraday lecture delivered before the Fellows of the Chemical Society in the Theatre of the Royal Institution, on Tuesday, June 4th, 1889.)
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Mendeleev's Periodic Principles |
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See also: Development of the Periodic Table, de Chancourtois, Dobereiner, Mendeleev, Moseley, Newlands, Seaborg
