Solution:
An element with the atomic number 17 belongs to the 3rd period and 17th group.Chlorine is the element with atomic number 17, a member of the 17th group and third period. 2,8,7 is the electronic configuration of the element whose atomic number is 17, as it has 7 valence electrons. So it belongs to the 17th group and 3rd period. Elements of group 17 are chlorine, fluorine, bromine, and iodine. The electrical structure of the element with atomic number 17 is two, eight, and seven. As a result, it has seven valence electrons.
