Knowing more on Resonance Structures of NO3– Ion

History of resonance–

The concept was introduced in 1899 by Johannes Thiele in his “Partial Valence Hypothesis” to explain benzene’s exceptional stability, which contradicted August Kekulé’s 1865 structure with alternating single and double bonds. In contrast to alkenes, benzene undergoes substitution reactions rather than addition reactions. He hypothesized that benzene’s carbon-carbon bond is a hybrid of a single and double bond. Additionally, the resonance hypothesis helped to explain the existence of isomers of benzene derivatives. For instance, Kekulé’s structure predicts four dibromobenzene isomers, including two ortho isomers in which the brominated carbon atoms are connected through a single or double bond. In reality, there are only three dibromobenzene isomers and only one is ortho, consistent with the concept of a single type of carbon-carbon bond halfway between a single and a double bond. 

Electrons do not have a fixed position in atoms, compounds, or molecules, but they do have probabilities of being found in certain regions (orbitals). Resonance forms depict places with a higher probability of occurrence (electron densities). This is analogous to holding your hat in either your right or left hand. When two or more possibilities exist, the term resonance is used.

When a Lewis structure for a single molecule is insufficient to completely represent the bonding between surrounding atoms in comparison to empirical data on the actual bond lengths between those atoms, resonance structures are used. A resonance hybrid is defined as the total of legitimate resonance structures, which indicates the overall delocalization of electrons within the molecule. A molecule with multiple resonance structures is more stable than one with fewer resonance structures. Certain types of resonance structures are more advantageous than others.

The phrase “resonance structure” refers to a collection of two or more Lewis Structures that together describe the electronic bonds and charges of a single polyatomic species. Resonance structures are capable of explaining delocalized electrons that cannot be represented by a single Lewis formula employing an integer number of covalent bonds.

Even when formal charges are considered, certain molecules or ions’ bonding cannot always be explained by a single Lewis structure. The term “resonance” refers to delocalized electrons inside certain compounds or polyatomic ions whose bonding cannot be described by a single Lewis formula. Numerous auxiliary structures are employed to illustrate a molecule or ion with such delocalized electrons (also called resonance structures or canonical forms).

There are three lone pairs (in the final shell) in two oxygen atoms and those oxygen atoms in the Lewis structure of the NO3– ion. Additionally, those two oxygen atoms have a negative charge.

There is one additional oxygen atom. The oxygen atom is coupled to the nitrogen atom through a double bond, and its final shell contains two lone pairs. Additionally, that oxygen atom has no charge.

There are no lone pairs on the nitrogen atom. However, the nitrogen atom has a positive charge.

How to draw resonance structure of NO3– ion-

The NO3– ion has three distinct resonance configurations. The nitrogen atom is double-bonded to oxygen in the first, whereas the oxygen atoms are single-bonded to one another. The nitrogen atom is single-bonded to oxygen in the second, whereas the oxygen atoms are double-bonded to one another. The nitrogen atom is double-bonded to oxygen in the third, whereas the oxygen atoms are single-bonded to one another.

There is no Lewis structure for NO2– in which nitrogen is an octet and both bonds are equal. Rather than that, we employ the concept of resonance: if two or more Lewis structures with the identical arrangement of atoms can be described for a molecule or ion, the actual electron distribution is an average of the Lewis structures. The real electron distribution in each nitrogen-oxygen bond in NO2– is a combination of a double bond and a single bond. Individual Lewis structures are referred to as resonance forms. The molecule’s true electronic structure (the sum of the resonance forms) is referred to as a resonance hybrid of the separate resonance forms. Between Lewis structures, a double-headed arrow denotes that they are resonance forms. Thus, the NO2– ion’s electronic structure is as follows:

CONCLUSION- 

These fictitious formal charges serve as a guide for establishing the optimal Lewis structure. It is preferable to have a structure with formal charges as near to zero as possible. Resonance arises when two or more Lewis structures with similar atom configurations but distinct electron distributions can be written. The real electron distribution (the resonance hybrid) is a weighted average of the distribution represented by the various Lewis structures (the resonance forms).