Question

What is wrong with each of the following Lewis structures? Fix the problem and write a correct Lewis structure. a. \(: \ddot{N}=N=\ddot{0}\) : b. \(: \ddot{\mathrm{O}}-\ddot{\mathrm{S}}-\ddot{\mathrm{O}}=\) c. \(: \ddot{\mathrm{B}} \mathrm{r}-\ddot{\mathrm{B}} \mathrm{r}\) : d. \(: \ddot{\mathrm{O}}=\mathrm{Si}-\ddot{\mathrm{O}}\) :

Short answer

The correct Lewis structures should be: (a) \( N \equiv N \), (b) \( \ddot{O}=S=\ddot{O} \), (c) \( Br-Br \) with each bromine having three lone pairs, and (d) \( O=Si=O \) with each oxygen having two lone pairs.

Step-by-step solution

Analyze the Lewis Structure of Diatomic Nitrogen

The given structure for diatomic nitrogen is : \( \ddot{N}=N=\ddot{O} \) : First, notice that nitrogen is incorrectly bonded to oxygen. Nitrogen has 5 valence electrons and forms a triple bond when in a diatomic molecule to fulfill the octet rule. Also, the structure misrepresents the nitrogen and oxygen atoms by giving nitrogen a full octet and oxygen only six electrons, when it’s supposed to be the other way around. Oxygen should have the octet and nitrogen's share in the triple bond should provide them with the remaining electrons needed for the octet.

Correct the Lewis Structure of Diatomic Nitrogen

Correct the structure: Each nitrogen atom should have a triple bond between them, and should not be bonded to an oxygen in this case. Each nitrogen should also have a lone pair of electrons. This satisfies the octet rule for both nitrogen atoms. The corrected structure would be \( N\equiv N \) with no oxygen involved.

Analyze the Lewis Structure of Sulfur Dioxide

The given structure for sulfur dioxide is : \( \ddot{O}-\ddot{S}-\ddot{O}= \) The problem with this structure is that sulfur should have a total of six valence electrons, but it is only shown with four. Moreover, one of the oxygens has two pairs of dots (lone pairs) and a double bond, which constitutes 6 electrons instead of the complete 8 that it should have as per the octet rule.

Correct the Lewis Structure of Sulfur Dioxide

Correct the structure by giving sulfur a pair of electrons to complete its valence shell and rearrange the electrons to ensure both oxygen atoms fulfill the octet rule. The correct structure is: \( \ddot{O}=S=\ddot{O} \) with each double bonded oxygen having two lone pairs to complete its octet.

Analyze the Lewis Structure of Bromine Molecule

The given structure for the bromine molecule is : \( \ddot{Br}-\ddot{Br} \) : The problem here is that bromine has 7 valence electrons and thus each bromine atom in a diatomic bromine molecule should share a single pair (forming a single bond) to fulfill the octet rule. However, in the given structure, each atom is shown with three pairs of dots (lone pairs), leaving only one single shared bond, which only gives each bromine atom 7 electrons instead of the full octet.

Correct the Lewis Structure of Bromine Molecule

The correct Lewis structure for bromine molecule is a single bond between the bromine atoms and three lone pairs on each bromine, making the corrected structure: \( Br-Br \) with each bromine having three lone pairs to complete its octet.

Analyze the Lewis Structure of Silicon Dioxide

The given structure of silicon dioxide is : \( \ddot{O}=Si-\ddot{O} \) : Silicon has 4 valence electrons and can form four bonds. In the given structure, Silicon is only forming three bonds (a double bond with an oxygen atom and a single bond with the other), which does not satisfy its bonding capacity.

Correct the Lewis Structure of Silicon Dioxide

The correct structure for silicon dioxide involves silicon at the center forming double bonds with each oxygen atom, which satisfies both the silicon's need for four bonds and oxygen's octet rule. The correct Lewis structure will be \( O=Si=O \) with each oxygen having two lone pairs.

Key concepts

The Octet Rule

Understanding the octet rule is essential for drawing accurate Lewis structures. It states that atoms tend to form bonds in such a way that each atom has eight electrons in its valence shell, giving it the same electron configuration as a noble gas. The octet rule is based on the observation that elements are especially stable when they have a full set of electrons in their outermost shell.

When examining Lewis structures, the octet rule guides us to identify mistakes. For instance, in the exercise where nitrogen and oxygen were incorrectly bonded, the error was clear because oxygen lacked the full octet. Similarly, sulfur in the sulfur dioxide molecule did not exhibit the expected six valence electrons. Each element's tendency to adhere to the octet rule lies at the heart of correct Lewis structures, and most elements of the main groups (excluding hydrogen and helium) follow this rule in chemical bonding.

Valence Electrons

Valence electrons are the electrons in the outermost shell of an atom and are vitally important because they participate in chemical bonds. The number of valence electrons determines how an atom will interact with others to form molecules. In creating correct Lewis structures, counting valence electrons enables us to establish proper bond formation and ensure that atoms attain a stable electronic configuration.

For instance, in the exercise solution for diatomic nitrogen, we account for each nitrogen atom having five valence electrons. These electrons dictate that the two nitrogen atoms will form a triple bond to share enough electrons to satisfy the octet rule for each atom. Understanding the concept of valence electrons ensures we create accurate representations of molecular structures and assists with identifying errors in existing diagrams.

Diatomic Molecules

Diatomic molecules are composed of two atoms, which may be of the same or different chemical elements. The term 'diatomic' literally means 'two atoms.' These molecules, such as O₂, N₂, and H₂, are a fundamental class of molecules in chemistry. In such molecules, each atom typically shares electrons with the other to obtain a stable electron configuration, usually following the octet rule for main-group elements.

During the analysis of the bromine (Br₂) structure in the exercise, recognizing that bromine forms diatomic molecules allowed us to realize that the Lewis structure should show a single bond between the two bromine atoms. This bond ensures that each bromine atom fulfills the octet rule. The understanding of diatomic molecules is crucial to draw correct Lewis structures for these types of compounds accurately.