Chapter 8, Problem 93AP

Interpretation Introduction

Interpretation:

The resonance structures of the ${\text{N}}_3^{-}$ ion are to be drawn, and the formal charges on them are to be shown.

Concept introduction:

For many molecules, it is impossible to explain all their properties by a single Lewis structure. In such a case, more than one Lewis structure is drawn to explain the properties. Such structures of a compound are called resonating structures, and this phenomenon is called resonance.

Resonating structure are represented by double headed arrow.

Resonance structure differs only in the position of their electrons, not in the positions of their atoms.

Resonance structures are hypothetical and cannot be isolated.

The rules for drawing the resonance structures are as follows:

Only lone pair of electrons and pi electrons can participate in conjugation in the formation of various resonating structures.

The single bonds present in the molecule do not break or form in the resonance structures.

The placement of atoms present in the molecule remains fixed.

The octet of all atoms is completely filled.

Due to the attraction toward electrons, the ions and molecules get some charge on them, which is called formal charge.

The formal charge is given by:

Formal charge = Total number of valence electrons in a free atom –total number of associated electrons.