In this lab, we explored some of the ideas that allowed Dmitri Mendeleev to publish his periodic table in 1869 including the findings of Johnann Dobereiner, John Newland and Lothar Meyer. This lab was completed utilizing element cards that displayed the name, atomic number, atomic mass and chemical formulas of the 64 elements that were known in the nineteenth century. We began by examining Dobereiner’s Triads by arranging the triads in order of atomic mass then calculated the average of the first and third element and compared it to the middle element. In the case of chlorine (35.5amu), bromine (80amu) and iodine (127amu), the average of chlorine and iodine is 81.3amu, which is very close to the atomic mass of bromine. We discovered this is