What are magic numbers?

What is valency of an element?

What is the number of groups in: (i) p-block  (ii) d-block?

How many elements are present in:
(i) second period    
(ii) fourth period    
(iii) sixth period?

Which property is the basis of long form of periodic table?

How many elements are placed in each period of the p-block?

Gallium was named by Mendeleev as

Give the ‘liquid elements’ in the periodic table.