Mendeleev put together the periodic table on the basis of known properties about atoms, specifically the atomic mass, equivalent mass and valency. This method revealed repetitive, or periodic, patterns among the elements that suggested an inherent organization. In some cases, the measured atomic mass of an atom conflicted with its predicted position in Mendeleev's periodic table. In these situations, Mendeleev correctly assumed that the measurement was wrong, and he successfully estimated the correct atomic mass.