Question

Which elements have electron configurations that end in ns2np5?

Answer 1

Explanation:

The given configuration is $ns^{2}np^{5}$ 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 $1s^{2}2s^{2}2p^{5}$.

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 $ns^{2}np^{5}$.

Answer 2

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.