By 1860, more than 60 elements were known. These last few decades brought to light heavy elements, adding more to our periodic table. Currently, there are over 120 known elements. I have investigated different sources to determine the mass of the heavies man-made element. The contradiction among the sources can be attributed to the time that these works were published.
Some sources are older than others and since then newer and heavier elements have been discovered.
I have determined the mass of Ununbium, which is element 112, as the mass of the heaviest element since it is the most recent. Physics News . Ninov, V. et al. Observation of Superheavy Nuclei Produced in the Reaction of 86 Kr with 208 Pb . Physical Review Letters .