Question

Draw all the possible resonance structures for \(\mathrm{N}_{2} \mathrm{O}\) and assign formal charges. Which resonance structure contributes the greatest amount to the resonance hybrid?

Short answer

The greatest contributor is Structure 1 with formal charges: N(0), N(+1), O(-1).

Step-by-step solution

Count Total Valence Electrons

Nitrogen (N) has 5 valence electrons and Oxygen (O) has 6 valence electrons. The formula for nitrous oxide is \( \mathrm{N}_2\mathrm{O} \), so we have two nitrogen atoms and one oxygen atom. Thus, the total number of valence electrons is: \( 2(5) + 6 = 16 \) electrons.

Draw Initial Lewis Structure

To construct the initial Lewis structure, start by arranging atoms:- Place the two nitrogen atoms and oxygen in a linear arrangement: \( \mathrm{N} - \mathrm{N} - \mathrm{O} \)- Use single bonds initially and distribute remaining electrons to complete octets where possible. Adjust bonds for optimal structures.

Draw Resonance Structure 1

Construct the first possible structure:- Double bond between first N and second N; triple bond between second N and O.- Check formal charges: First N (0), second N (+1), O (-1).- Total formal charge: \( 0 + 1 - 1 = 0 \).

Draw Resonance Structure 2

Construct the second structure:- Triple bond between first N and second N; single bond between second N and O.- Check formal charges: First N (-1), second N (+1), O (0).- Total formal charge: \( -1 + 1 + 0 = 0 \).

Draw Resonance Structure 3

Construct another possibility:- Single bond between first N and second N; double bond between second N and O.- Check formal charges: First N (+1), second N (0), O (-1).- Total formal charge: \( 1 + 0 - 1 = 0 \).

Evaluate Dominant Resonance Structure

Among the three structures, the one with the least separation of charges and minimizing non-zero formal charges is most stable. Here, structure 1 (0, +1, -1) is preferred as it places the (-) charge on the more electronegative oxygen, making it more stable compared to the others where charges are less optimal.

Key concepts

Formal Charges

Formal charges help us determine the most stable resonance structure and are crucial in understanding molecular stability.
They are hypothetical charges assigned to atoms within a molecule to help track electron distribution.To calculate formal charges:

• Identify the number of valence electrons for each atom by looking at its original state based on the periodic table.
• Subtract the number of non-bonding electrons (lone pairs) associated with that atom.
• Subtract half the number of bonding electrons (shared electrons).

Mathematically, this is expressed as:\[\text{Formal Charge} = \text{Valence Electrons} - (\text{Non-bonding Electrons} + \frac{1}{2}\text{Bonding Electrons})\]Using formal charges, we assess which resonance structure of nitrous oxide (\( N_2O \)) is favored. Structures with formal charges closest to zero are generally more stable.
The preferred structure should minimize charge separation and any negative charge is ideally located on the most electronegative atom.

Lewis Structures

Lewis structures are diagrams that represent the arrangement of electrons in a molecule.
They showcase the bonding between atoms and the lone pairs of electrons that may exist.To draw a Lewis structure:

• Determine the total number of valence electrons for the molecule.
• Choose a skeletal structure, keeping in mind that the least electronegative atom typically occupies the central position.
• Create single bonds between atoms and then distribute the remaining electrons to satisfy the octet rule where possible.
• If necessary, adjust bonds to create double or triple bonds to fulfill the octet rule for each atom.

In the case of \( N_2O \), start with a straightforward linear arrangement: \( N-N-O \).
Modify and adjust bonds to explore different resonance structures while assessing the formal charges.
This way, you find the most stable configuration, which is vital for predicting molecular behavior.

Nitrous Oxide (N2O)

Nitrous oxide, commonly known as laughing gas, is a chemical compound with a linear molecular structure composed of two nitrogen atoms and one oxygen atom.
It is crucial to understand its electron configuration to determine the stability and chemical behavior of the molecule.Here are some peculiar characteristics of \( N_2O \):

• The molecule contains a total of 16 valence electrons, calculated from its constituent atoms.
• Generally, the central nitrogen in \( N_2O \) resonates between different structures, minimizing potential energy and maintaining chemical stability.
• The dominant resonance structure features a double bond between the nitrogen atoms and a triple bond between the nitrogen and oxygen, placing a negative formal charge on the oxygen.

Understanding its resonance structures provides insight into the electron distribution across the molecule.
It also supports the prediction of its chemical reactions and properties such as its role in anesthesia and its use as a propellant in rockets.