There are `2, 8` and `8` elements in the first, second and third periods of periodic table respectively. Explain.

The number of elements in 5th and 6th period of periodic table are respectively

Name the elements included in the first period of the periodic table.

How many elements are there in first period in the periodic table ?

Name the elements in correct order of their increasing atomic numbers present in the first, second and third short periods of the periodic table. State each elements electronic configuration.

The atomic radii of the elements across the second period of the periodic table -

The number of elements in the first periods of the modern periodic table is ________

Answer the following questions: How many elements are there in the second and the third periods of the periodic table ?