Why did mendeleev organize the periodic table according to mass?

Answer 1

Back in Mendeleev's time (late 1800's), scientists knew nothing at all about quantum mechanics and the structure of the atom. Therefore, they didn't know about how each element is different by 1 proton as we go across a period. Instead, Mendeleev arranged the elements by atomic weight- which could be done using scales and mathematics. His predictions were largely accurate- and it's his version of the table that makes up the modern form today.

Answer 2

When Mendeleev first organized his Periodic Table in 1869, Ernest Rutherford had yet to discover the nucleus of the atom and the proton. Modern periodic tables are organized by atomic number, or the number of protons in the nucleus of each atom of the element. Since the concept of an atomic number was unknown, Mendeleev used the logical order that was available to him - atomic mass.

Answer 3

As Mendeleev did not know about Atomic Numbers at this point, only mass numbers.

Answer 4

The atomic numbers of the elements were not known until the early 1900s. Dmitri Mendeleev presented his periodic table in which the elements were ordered by atomic weight in 1869.

Answer 5

At the time essentially nothing was known about atomic structure. The concept of atomic number didn't come until later, but Atomic Mass was relatively easy to determine.

Answer 6

Because it was much easier to organize.

Answer 7

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