Question

What is a nonbonding electron domain $?$
 $(i)$ A lone pair of electrons
 $(ii)$ An area of electron density
 $(iii)$ A double bond
 $(iv)$ The area of electron density in anion

Answer 1

Hint: Nonbonding electron domain is related to the electrons which generally do not take part in the bonding electrons. Bonding electrons are those which involve making the bond with other atoms. Non-bonding electron domain is the domain of all such electrons which do not involve bonding electrons.

Complete answer:
Any atom makes a bond with another atom in three ways. Firstly when a single atom donates the electron pair to another element then it forms an ionic bond. Secondly when there is mutual sharing of electrons between the two atoms then it is known as covalent bond. Thirdly when there is no mutual sharing of electrons to another atom then this is known as co-ordinate bond. In all of these bond making processes, not all the valence electrons of an atom take part. Only a few electrons take part while forming a bond. Those valence electrons which do not take part in the bond making process are called non-bonding electrons. Thus these electrons are present as lone pairs after the bond making process. These electrons have no involvement in the bond present in between the two atoms. Thus the correct option is $(i)$ . According to which, these non-bonding electrons are available in the form of lone pairs.

Note:
These non-bonding electrons can affect the physical and chemical properties of the elements. When these lone pairs are involved in the bond making process with some other atom, then they will be counted as bonded electrons. A co-ordinate bond is also a special type of covalent bond. In covalent bond there is mutual sharing of electrons between atoms but in co-ordinate bond there is no mutual sharing of electrons between the atoms.