A Pattern of properties appeared when he arranged the elements in order of increasing Atomic Mass
A Pattern of properties appeared when he arranged the elements in order of increasing Atomic Mass
Generally the term "atomic mass" is used for isotopes. For elements is preferred now "atomic weight".
No two elements may have the same atomic number. But two elements may have same atomic mass. Hence atomic number is better than atomic mass.
By Atomic Mass
The molar mass of a compound is the sum of atomic weights of the contained elements in the molecule.The expression atomic weight is correct for elements; for isotopes is correct atomic mass.
Gold is a meta element. Atomic Mass of it is 197.
Atomic Mass.
Iron is a metal element. Atomic mass of it is 55.84.
I suppose that you think to atomic weights (not mass) of chemical elements and the molecular mass.
Mendeleev arranged the elements in the periodic table according to their atomic masses.
Mendeleev arranged elements in order of atomic mass. He arranged elements in rows and columns that later helped in discovering modern periodic table.