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Elements which are similar as regards their chemical properties have atomic weights which are either of nearly the same value (eg. Pt, Ir, Os) or which increase regularly (eg. K, Ru, Cs).

Certain characteristic properties of elements can be foretold from their atomic weights.

The body tends to treat elements in the same column of the periodic table as equivalents.

The elements, if arranged according to their atomic weights, exhibit an apparent periodicity of properties.

Moreover, the abundance of chemical compounds and their importance in daily life hindered the chemist from investigating the question, in what does the individuality of the atoms of different elements consist.

The most common and most important result of them is that the nature and size of the effect on corresponding series of different elements are largely an expression of the peculiarity of their atomic structure - or, at least, of the structure of the surface.

Experimental work of great refinement is necessary in order to determine atomic weights. No relationships between them have yet been certainly found which make it possible for us to compute by any sort of calculation exactly the value of any one atomic weight from any other.

The discovery of various phenomena has led to a recognition of the fact that the chemical atom is an individual which again is itself made up of several units into a selfcontained whole.

The elements which are the most widely diffused have small atomic weights.

The atoms may be compared to the letters of the alphabet, which can be put together into innumerable ways to form words. So the atoms are combined in equal variety to form what are called molecules.