Question

atomic number of calcium is 20 and oxygen is 8
which are the periods is which they belong to ?​

Answer 1

Answer:

Calcium (Ca) belongs to 4th period.

Oxygen (O) belongs to 2nd period.

Explanation:

I think it doesn't need any explanation just a simple common sense and periodic table :D.

Answer 2

Refer to the attachment in order to see their location.

A period in the periodic table is a row of chemical elements. Additionally, all elements in a row have the same number of electron shells and hence, Oxygen belongs to Group 16 of Period 2 and Calcium belongs to Group 2 of Period 4.