Question

Draw Lewis structures for each of the following molecules. Show resonance structures, if they exist. a. \(\mathrm{O}_{2}\) b. \(\mathrm{N}_{2}\) c. \(\mathrm{CO}\) d. \(\mathrm{SO}_{2}\)

Short answer

Lewis structures: \(\text{O}_2 = \text{O}=\text{O}\), \(\text{N}_2 = \text{N}\equiv\text{N}\), \(\text{CO} = \text{C}\equiv\text{O}\), \(\text{SO}_2 = \text{O}=\text{S}-\text{O}\) \leftrightarrow \(\text{O}-\text{S}=\text{O}\).

Step-by-step solution

Draw the Lewis Structure for \(\text{O}_2\)

Oxygen has 6 valence electrons. \(\text{O}_2\) has a total of 12 valence electrons (6+6). Draw the atoms with a double bond between them and distribute the remaining electrons as lone pairs: \(\text{O}=\text{O}\).

Draw the Lewis Structure for \(\text{N}_2\)

Nitrogen has 5 valence electrons. \(\text{N}_2\) has a total of 10 valence electrons (5+5). Draw the atoms with a triple bond between them and distribute the remaining electrons as lone pairs: \(\text{N}\equiv\text{N}\).

Draw the Lewis Structure for \(\text{CO}\)

Carbon has 4 valence electrons, and oxygen has 6 valence electrons. \(\text{CO}\) has a total of 10 valence electrons (4+6). Draw the atoms with a triple bond between them and distribute the remaining electrons as lone pairs: \(\text{C}\equiv\text{O}\).

Draw the Lewis Structure for \(\text{SO}_2\)

Sulfur has 6 valence electrons, and each oxygen has 6 valence electrons. Therefore, \(\text{SO}_2\) has a total of 18 valence electrons (6+6+6). The molecule has resonance structures. One common structure is: \(\text{O}=\text{S}-\text{O}\), with 2 lone pairs of electrons on sulfur and each oxygen. The resonance structures can be represented as: \(\text{O}=\text{S}-\text{O}\) \leftrightarrow \(\text{O}-\text{S}=\text{O}\).

Key concepts

Valence Electrons

Valence electrons are the outermost electrons in an atom. They play a crucial role in chemical reactions and bonding. For example, oxygen (O) has six valence electrons, while nitrogen (N) has five. In a Lewis structure, valence electrons are represented by dots around the chemical symbol. Understanding the number of valence electrons helps predict how atoms will bond. In the molecules \(\text{O}_2\), \(\text{N}_2\), \(\text{CO}\), and \(\text{SO}_2\), valence electrons determine the type of bonds and the structure.

Resonance Structures

Resonance structures are different ways of placing electrons among atoms in a molecule. They showcase the delocalization of electrons within the molecule. A molecule like \(\text{SO}_2\) can have more than one valid Lewis structure. These alternative structures are represented using double-headed arrows (\( \leftrightarrow \)). For \(\text{SO}_2\), the electrons can be arranged as \( \text{O} = \text{S} - \text{O} \leftrightarrow \text{O} - \text{S} = \text{O} \).

Chemical Bonds

Chemical bonds form when atoms share or exchange electrons. The main types are ionic and covalent bonds. In the Lewis structure for \(\text{O}_2\), a double bond is present, meaning two pairs of electrons are shared. \(\text{N}_2\) has a triple bond, with three pairs of electrons shared. These bonds help stabilize the molecules. In \(\text{CO}\), a triple bond also exists between carbon and oxygen, indicating a strong bond due to shared electrons.

Molecular Geometry

Molecular geometry refers to the 3D arrangement of atoms in a molecule. The shape affects the molecule's properties and reactivity. For instance, \(\text{O}_2\) is linear because of its double bond, giving it a straight-line shape. \(\text{N}_2\) is also linear, with its three shared electron pairs pulling the atoms directly towards each other. \(\text{SO}_2\) is bent due to its resonance structures and the lone pairs on sulfur. Identifying shapes helps predict how molecules interact.