Nitrous oxide (N 2 O) has three possible Lewis structures: Given the following bond lengths, N—N 167 pm N9N 120 pm N:N 110 pm N9O 115 pm N—O 147 pm rationalize the observations that the N—N bond length in N 2 O is 112 pm and that the N—O bond length is 119 pm. Assign formal charges to the resonance structures for N 2 O. Can you eliminate any of the resonance structures on the basis of formal charges? Is this consistent with observation?

Interpretation: The observation that the N−N bond length in N2O is 112 pm and that the N−O bond length is 119 pm to be explained. The elimination of any resonance structure of N2O on the basis of formal charge is to be identified. The consistency of this elimination is to be checked with the given observation.

Concept introduction: The Lewis structure is also known as dot structure. This structure depicts the bonding between atoms and the lone pairs of electrons if exists.

Formal charge is a charge given to an atom with assumption that electrons are shared equally between atoms in all chemical bonds irrespective of their electronegativity.

To determine: The rationalization of the observation that the N−N bond length in N2O is 112 pm and that the N−O bond length is 119 pm; if any of the resonance structure of N2O can be eliminated on the basis of formal charge; if this elimination is consistent with the given observation.

To determine: The rationalization of the observation that the N−N bond length in N2O is 112 pm and that the N−O bond length is 119 pm.

Generally, nitrogen atom forms triple bond with other elements and oxygen atom forms two bonds with other elements. The overall bond length of N−N is 112 pm. Since, the given bond length of N≡N bond is 110 pm and nitrogen atom mostly forms triple bond with other atoms, yet N−N and N=N bond also exists. The average of these bond lengths is close to 112 pm.

Correspondingly, oxygen atom mostly forms two bonds with other elements. Hence, the bond length of N−O falls down to 119 pm as it is the average of more stable N=O bond and less stable N−O bond.

To determine: If any of the resonance structure of N2O can be eliminated on the basis of formal charge.

The N2O molecule has three resonance structures,

Figure 1

Formula

The formula of formal charge is,

Formal charge =V−[N+B2]

Where,

• V is number of valence electrons.
• N is number of non-bonding valence electrons.
• B is total number of bonds shared with other atoms in the given molecule.

The formal charge of first (I) Lewis structure is calculated as,

For central nitrogen (N) atom,

Formal charge =5−[0+(12×8)]=+1

For terminal nitrogen (N) atom,

Formal charge =5−[4+(