how was mendeleev able create the periodic table if atomic mass wasn't known till the next century?

Question

This question was proposed in my chem class, because the first periodic table(which was based on atomic mass) appeared in 1869, however atomic mass wasn't found till 1913. Currious?

Answer 1

He didn't necessarily know the atomic weights of the individual elements; however, he organized them according to observed physical properties and his greatest contribution was the prediction of elements yet unknown to fill in "holes" in the table.

Answer 2

Mendeleyev did have information about the proportions that the elements reacted with oxygen. They had this information for some time, by decomposing oxides of the elements, or by oxidizing the pure elements (circa 1770’s and 1780’s). Joseph Priestly was THE MAN.

Mendeleyev grouped the compounds into similar families that shared the same proportions of oxygen. Then within the families it is an easy task to rank based upon density of either pure substance or oxide.

BTW it is OK to rank one of these answers as best answer.

Answer 3

What Mendeleev specified was atomic weight, by which he meant combining weight (equivalent weight multiplied by valence). These were laboratory-determined weights since the time of Proust in Spain in the 1700's. Actually, the quirks of distributions of stable isotopes of one or two elements in nature meant that atomic weights were "out of order." So only when atomic number was used could the modern periodic law be formulated. "The chemical properties of the elements are periodic functions of their atomic numbers."

Answer 4

You are incorrect. Atomic mass has been a standard since Avogadro's research. ATOMIC NUMBER however is a newer institution, as Mendeleev's periodic table was actually ordered by atomic mass, yet today it is ordered by atomic number.

Upon inspection, tellurium's atomic mass is actully greater than bromine's. Orginally they were reversed.

Answer 5

He did it all by just grouping them with similar properties, the periodic table is still like that today, there are some exceptions to the incresing atomic weight. Example of this is Argon to Potasssium

Answer 6

I would assume that the very first periodic table dosnt look like the one we have today his table probably didnt include mass just as it didn't include some elements

just my assumption Did i mess up?