Atomic number of element present in the third period and seventeenth group of periodic table

Explanation

The third period involves the filling of only 3s- and 3p-orbitals. Therefore, this period consists of only 2s- and 6p-block elements. The third period starts with Z = 11 and ends at Z = 18. Therefore, the elements with Z = 11 and Z = 12 would belong to s-block. The next six elements with Z = 13 (group 13) to Z = 18 (group 18) are p-block elements. Therefore, the element belonging to group 17 must have atomic number Z = 17.