Question

Where hydrogen should be placed in modern periodic table? give reason?

Answer 1

It should be placed in 1 group and first period as according to modern periodic law the properties of the elements and their compounds are a periodic function of their atomic numbers. Thus, in the modern periodic table, atomic number (which is equal to the nuclear charge) forms the basis of the classification of elements.
Hydrogen has 1 atomic number so it should be placed as stated.