What is periodic table? What do you mean by classification of elements?

What was the need for the classification of elements?

Discuss the earlier attempts to classify elements.

Which important property did Mendeleev use to classify the elements in his Periodic Table? and did he stick to that?

What is the basis of Mendeleev's Periodic table?

Give a brief discussion of the Mendeleev's Periodic table. 

What are the merits and applications of Mendeleev's Periodic table?

State and explain Modern Periodic Law.

What is periodicity? What is its cause?