Question

what is the number of elements in first, second and third period of periodic table? give reason for your answer. (3 marks)

Answer 1

The number of elements in the first period are 2. (This period is hence known as a short period.) (2 s-block elements)
The number of elements in the second period are 8.( 2 s-block elements and 6 p-block elements)
The number of elements in the third period are 8. ( 2 s-block elements and 6 p-block elements)

Answer 2

Answer:

the number of element in the the first and third period of the modern periodic table.

Explanation:

(1) the number of element in the first period are are-2

(2) the number of element in the period third are-8