When russian chemistry professor dmitri mendeleev published the first periodic table in 1869, he was trying to organize all known elements in a way that would his students learn chemistry. describe three features of the periodic table's organization. for each feature, identify one way that that the feature you understand and study the elements.

The features of Mendeleev's periodic table which helped us to understand whole periodic table was:

1) Atomic masses. - He arranged all the known elements in increasing order of their atomic mass, atomic mass is quite similar to atomic number (just plus number of neutrons) so, he did from simpler to complex elements, so he sorted his table.

2) Formation of oxides. - He checked for the formation of oxides, and the elements which can form similar oxides, he placed them in a same family (group)

3) Assumed for unknown element. - He just left the place for unknown element, it was the application of other two concepts which i described above, specific atomic mass with no oxides, would create an empty place. So, he just assumed, that element will be discovered in future & he had to left the place.

Hope this helps! 

It shows that the experiment is designed properly.