chemistry

state the law of Octaves

what was the limitations of  Dobereiner's classifications?

what was the major limitation of Mendleeve's periodic table ?

2. name three elements whose atomic masses were corrected on the basis of their position in mendeleev's periodic table.

3.elements of group III A and V A in the Mendleev's Periodic table have the same general formula of their hydride's  (RH3). how are they placed in different groups in Mendeleev's periodic table ?

4. why did Mendleev's leave some gap in his periodic table?

5. in group VIII of periodic table, why does Cobalt with atomic mass 58.93 appear before Nickel having atomic mass 58.71 ?

6. (a) If we take Beryllium as the first element then which will be the eighth element from it according to Newland's law of Octaves ?
    (b) Did Mendeleev include noble gasses in his periodic table?

7. (a) what physical and chemical  properties of elements were used by Mendeleev in creating his periodic table ?
  (b) What were the two major shortcoming of Mendeleev's periodic table?

8. (a) Why could