Text: a) The elements, if arranged according to their atomic weights, exhibit an obvious periodicity of properties. b) The atomic weight determines the character of the element just as the magnitude of the particle determines the properties of a complex body. Therefore, for example, S and Te, Cl, and I, etc., exhibit very obvious differences as well as similarities. c) We must expect the discovery of many yet unknown elements, for example, elements analogous to Al and Si, whose atomic weight would be between 65 and 75. d) The atomic weight of an element may sometimes be amended if its analogues are known. e) Certain analogues of the elements can be foretold from their atomic weights. (Medeleyev, 1869)

See Also: LAW OF PROPORTION; LAW OF LINEAR DIMENSIONS; LAW OF OCTAVE; LAW OF ELECTRO-CHEMICAL EQUIVALENCE

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