Textbook Question
The reaction of Fe2O3(s) with Al(s) to form Al2O3(s) and Fe(s) is called the thermite reaction and is highly exothermic. What role does lattice energy play in the exothermicity of the reaction?
Ch.9 - Chemical Bonding I: The Lewis Model
Chapter 9, Problem 96
Phosgene (Cl2CO) is a poisonous gas used as a chemical weapon during World War I. It is a potential agent for chemical terrorism today. Draw the Lewis structure of phosgene, including all three resonance forms by alternating the double bond among the three terminal atoms. Which resonance structure is the best?
Verified step by step guidance1
insert step 1> Start by counting the total number of valence electrons in phosgene (Cl2CO). Chlorine has 7 valence electrons, carbon has 4, and oxygen has 6. Therefore, the total number of valence electrons is 2(7) + 4 + 6 = 24 valence electrons.
insert step 2> Draw a skeletal structure with carbon as the central atom, since it is less electronegative than oxygen and chlorine. Connect the carbon atom to the two chlorine atoms and the oxygen atom with single bonds.
insert step 3> Distribute the remaining valence electrons to satisfy the octet rule for each atom. Start by placing lone pairs on the terminal atoms (Cl and O) to complete their octets.
insert step 4> Consider the possibility of resonance structures by moving a lone pair from the oxygen atom to form a double bond with the carbon atom. This will create a resonance structure. Repeat this process by forming a double bond between carbon and each chlorine atom, one at a time, to generate all possible resonance structures.
insert step 5> Evaluate the resonance structures based on formal charges. The best resonance structure is the one where the formal charges are minimized and the negative charge, if any, is on the most electronegative atom. Calculate the formal charges for each atom in all resonance structures to determine the most stable one.
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lewis Structures
Lewis structures are diagrams that represent the bonding between atoms in a molecule and the lone pairs of electrons that may exist. They use dots to represent valence electrons and lines to represent bonds. Understanding how to draw Lewis structures is essential for visualizing molecular geometry and predicting reactivity.
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Lewis Dot Structures: Ions
Resonance Structures
Resonance structures are different ways of drawing the same molecule that illustrate the delocalization of electrons. In molecules like phosgene, resonance helps to depict how electrons can be distributed across different bonds. The actual structure of the molecule is a hybrid of these resonance forms, which contributes to its stability and reactivity.
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01:42Resonance Structures
Resonance Stability
The stability of resonance structures is determined by factors such as the octet rule, formal charges, and the overall energy of the structure. The most stable resonance structure typically has the least formal charge and satisfies the octet rule for all atoms. Identifying the best resonance structure is crucial for predicting the behavior of the molecule in chemical reactions.
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Related Practice
Textbook Question
NaCl has a lattice energy of -787 kJ/mol. Consider a hypothetical salt XY. X3+ has the same radius of Na+ and Y3- has the same radius as Cl-. Estimate the lattice energy of XY.
Textbook Question
The cyanate ion (OCN-) and the fulminate ion (CNO-) share the same three atoms but have vastly different properties. The cyanate ion is stable, while the fulminate ion is unstable and forms explosive compounds. The resonance structures of the cyanate ion are explored in Example 9.8. Draw Lewis structures for the fulminate ion—including possible resonance forms— and use formal charge to explain why the fulminate ion is less stable (and therefore more reactive) than the cyanate ion.
Textbook Question
Draw the Lewis structure for each organic compound from its condensed structural formula. a. C3H8 d. CH3COOH
Textbook Question
Draw the Lewis structure for each organic compound from its condensed structural formula. b. CH3OCH3