Question

What is the basic theme of organisation in the periodic table?
Which important property did Mendeleev use to classify the elements in his per
table and did he stick to that?
What is the basic difference in approach between the Mendeleev's Periode
and the Modern Periodic Law?​

Answer 1

1)Mendeleev considered physical and chemical property of elements.

2) Mendeleev make periodic table on basic of atomic mass of atom and in modern periodic table is based on atomic number of a atom