Respuesta :
Last level of atoms of these elements has 2+5= 7 electrons. These elements are located in the 17th group of the Periodic Table, and they are called halogens.
Explanation:
The given configuration is [tex]ns^{2}np^{5}[/tex] and this shows that there are seven valence electrons present in the outermost shell. Therefore, it is a general configuration of group 17 which is also known as halogen group.
Elements of group 17 are fluorine, chlorine, bromine, iodine and astatine.
For example, fluorine is a group 17 element that has electronic configuration [tex]1s^{2}2s^{2}2p^{5}[/tex].
Value of n will start from 2 and increases on moving down the group.
Hence, we can conclude that halogens are the elements that have electron configurations that end in [tex]ns^{2}np^{5}[/tex].
