Modern periodic law : 

‘The physical and chemical properties of elements are the periodic function of the electronic configurations of their atoms”.

Construction of the long form periodic table : 

1. Based on the modern periodic law, the modern periodic table is proposed. 

2. This periodic table is known as long form of the periodic table. 

3. Long form periodic table is the graphical representation of Aufbau principle.

4. The modern periodic table has 18 vertical columns called groups and 7 horizontal rows known as periods. 

5. There are 18 groups, represented by using Roman numerals I to VIII, with letters A and B in traditional notation, (or) 1 to 18 by Arabic numerals. 

6. There are 7 periods. These periods are represented by Arabic numerals 1 to 7. 

7. The number of main shells present in the atom of particular atom decides to which period it belongs. 

8. First period consists 2 elements, 2nd and 3rd periods contains 8 elements each, 4th and 5th periods contains 18 elements each, 6 period contains 32 elements and 7th period is incomplete. 

9. The elements are classified into s, p, d and f block elements. 

10. Inert gases are placed in 18th group.