What was the key characteristic by which dmitri mendeleev arranged his periodic table? a. increasing atomic number b. electron configuration c. decreasing atomic number d. increasing atomic mass

 D. increasing atomic mass

Explanation:  Dmitri Mendeleev  arranged the periodic table on the basis of the increasing atomic mass.

He observed the physical and chemical properties of the elements and he found that these properties are related to their atomic masses. Thus he arranged these elements on the basis of the physical and chemical properties into different kinds of groups.

Thus elements with similar property was arranged in the same group.

i believe the answer is a.