On 6 March 1869, Mendeleev made a formal presentation to the Russian Chemical Society, entitled The Dependence between the Properties of the Atomic Weights of the Elements, which described elements according to both atomic w

eight and valence. This presentation stated that

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

4. 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.

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

For his predicted eight elements, he used the prefixes of eka, dvi, and tri (Sanskrit one, two, three) in their naming. Mendeleev questioned some of the currently accepted atomic weights (they could be measured only with a relatively low accuracy at that time), pointing out that they did not correspond to those suggested by his Periodic Law.

stated that if the atomic weight of an element caused it to be placed in the wrong group, then the weight must be wrong. (He corrected the atomic masses of Be, In, and U)

was so confident in his table that he used it to predict the physical properties of three elements that were yet unknown.

Three drawbacks of Three drawbacks of Mendeleev's periodic tableMendeleev's periodic table