He discovered that each element has its own atomic number. Hence, option D is correct.
What is a periodic table?
The periodic table is a tabular arrangement of the chemical elements organized with an increasing atomic number.
Mendeleev arranged chemical elements in ascending order of atomic mass. This arrangement gave some problems to Mendeleev's table by the impression that some elements appeared to be out of place. An example was argon, whose relative atomic mass of 40 is the same as that of calcium.
In the early twentieth century, when Henry Moseley experimented with the x-ray spectrum of the elements, he found that all atoms of the same chemical element had the same nuclear charge, and therefore had the same number of protons. And it was concluded that the elements would be in an even more regular pattern when arranged in a table in order of their atomic number rather than atomic mass.
Thus, we can conclude that Moseley revised Mendeleev's periodic table by arranging the elements on the periodic table in ascending order of atomic number.
Hence, option D is correct.
Learn more about the periodic table here:
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