Question

Which of the following molecules is adequately represented by a single Lewis structure? (1) \(\mathrm{O}_{3}\) (2) NOCl (3) \(\mathrm{SO}_{2}\) (4) \(\mathrm{N}_{2} \mathrm{O}\)

Short answer

NOCl is the molecule that can be adequately represented by a single Lewis structure.

Step-by-step solution

- Understand Lewis Structures

Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. Some molecules can be adequately represented with a single Lewis structure, while others require resonance structures.

- Analyze \(\text{{O}}_{3}\)

Draw the Lewis structure for \(\text{{O}}_3\). It consists of 3 oxygen atoms connected in a chain. You will find that resonance forms are needed because the double bonds can move between different oxygen atoms.

- Analyze NOCl

Draw the Lewis structure for NOCl. Nitrogen (N), oxygen (O), and chlorine (Cl) are connected with single bonds, and the remaining electrons fill the octets. This molecule does not have different resonant structures, so it can be adequately represented by a single Lewis structure.

- Analyze \(\text{{SO}}_{2}\)

Draw the Lewis structure for \(\text{{SO}}_2\). It consists of a sulfur atom double bonded to two oxygen atoms. You will find that resonance forms are needed because the double bonds can be placed at either oxygen location.

- Analyze \(\text{{N}}_{2} \text{{O}}\)

Draw the Lewis structure for \(\text{{N}}_2 \text{{O}}\). It consists of two nitrogen atoms and one oxygen atom. This structure also involves resonance because the bonding between nitrogen atoms can vary in placement.

Key concepts

Resonance Structures

Resonance structures are multiple ways to depict a molecule using Lewis structures. These structures show different arrangements of electrons. Resonance occurs when electrons can move to different positions within the molecule, making it impossible to represent the molecule with one static structure. For instance, in \text{\(\mathrm{O}_3\)}, the double bonds can switch between the oxygen atoms.

This constant shifting helps to show the true nature of the electron distribution within the molecule. Resonance structures contribute to the overall stabilization of the molecule, known as resonance stabilization.

Molecular Bonding

Molecular bonding describes how atoms bind together to form molecules. Bonds are formed due to the attraction between atoms seeking stability by achieving a lower energy state. There are several types of bonds:

• Ionic bonds
• Covalent bonds
• Metallic bonds

Covalent bonds are particularly important for Lewis structures. They involve the sharing of electron pairs between atoms. Consider NOCl as an example: Nitrogen forms single covalent bonds with both oxygen and chlorine atoms, making it possible to represent the molecule with a single Lewis structure.

Electron Pairs

Electron pairs are pairs of electrons that occupy an orbital around an atom’s nucleus. They can be either bonding pairs or lone pairs:

• Bonding pairs: Shared between two atoms in a molecule to form a covalent bond
• Lone pairs: Not shared and remain on a single atom, affecting the molecule’s shape and reactivity

In Lewis structures, both types of electron pairs are crucial. For example, in \text{\(\mathrm{SO}_2\)}, sulfur shares electrons with two oxygen atoms (bonding pairs) and still holds lone pairs. These lone pairs impact the molecule's geometry and can also influence resonance structures.

Octet Rule

The octet rule states that atoms tend to form bonds to have eight electrons in their valence shell, achieving a stable configuration similar to noble gases.

This rule applies to most main-group elements. For instance, nitrogen in NOCl achieves its octet by sharing electrons with oxygen and chlorine, adhering to the octet rule. However, there are exceptions where molecules do not follow the octet rule, particularly involving elements beyond the second period that can have more than eight electrons due to the availability of d-orbitals.