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