Why did mendeleev leave blank spaces in his version of the periodic table? mendeleev’s periodic table arranged elements in order of increasing atomic mass; spaces were left for elements not having the correct atomic mass. mendeleev’s periodic table arranged elements in groups of similar chemical properties; spaces were left for elements not having a similar chemical property. mendeleev’s periodic table arranged elements in order of increasing atomic mass; it was noticed that chemical properties repeated. mendeleev predicted an element had not been discovered to fit the space.