Question

1. State and explain modern periodic table and modern periodic law?

2. How many periods in the modern periodic table?

3. Which is the shortest period?

4. Number of elements in the third period?

5. Total number of groups?

Answer 1

In 1913 Mosely through his x-ray diffraction experiments proved that the properties of elements depended on the atomic number not on the atomic mass. 

According to this the periodic law of Mendeleev and the periodic table were modified consequently the modern periodic table was prepared by arranging elements in the increasing order of atomic number. The modern periodic law states that the physical and chemical properties of elements are periodic function of their atomic number.

1.  7

2. I period

3. 8

4. 18