Which amongst the following elements whose atomic number is given below belong to the same period?
Give reason. 17, 10, 20, 12, 19, 15.
We will first write the electronic configuration of all the elements mentioned:
17:- 2,8,7
10:- 2,8
20:- 2,8,8,2
12:- 2,8,2
19:- 2,8,8,1
15:-2,8,5
So, the elements with atomic number
17, 12, 15 belong to the same period as they have the same number of the shell.
20, 19 belong to the same period as they have the same number of the shell.