Who arranged the elements according to atomic mass and used the arrangement to predict the properties of missing elements?
Mendeleev discovered that if the elements were arranged roughly in order of increasing atomic mass, their properties tended to show periodic trends; for instance, there was a regular, repeating appearance of highly reactive metals that form strong bases when combined with oxygen (alkali metals).
Mendeleev noted that for the periodic trends to work there had to be missing elements such as two then-undiscovered ones between zinc and arsenic. The later discovery of these relatively rare elements confirmed Mendeleev's hypothesis, and now the Periodic Table adorns scientific and engineering workplaces the world over.
Read more at https://en.wikipedia.org/wiki/Dmitri_Mendeleev.