Ch.9 - Bonding & Molecular StructureWorksheetSee all chapters
All Chapters
Ch.1 - Intro to General Chemistry
Ch.2 - Atoms & Elements
Ch.3 - Chemical Reactions
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
Ch.4 - Chemical Quantities & Aqueous Reactions
Ch.5 - Gases
Ch.6 - Thermochemistry
Ch.7 - Quantum Mechanics
Ch.8 - Periodic Properties of the Elements
Ch.9 - Bonding & Molecular Structure
Ch.10 - Molecular Shapes & Valence Bond Theory
Ch.11 - Liquids, Solids & Intermolecular Forces
Ch.12 - Solutions
Ch.13 - Chemical Kinetics
Ch.14 - Chemical Equilibrium
Ch.15 - Acid and Base Equilibrium
Ch.16 - Aqueous Equilibrium
Ch. 17 - Chemical Thermodynamics
Ch.18 - Electrochemistry
Ch.19 - Nuclear Chemistry
Ch.20 - Organic Chemistry
Ch.22 - Chemistry of the Nonmetals
Ch.23 - Transition Metals and Coordination Compounds
Sections
Chemical Bonds
Lattice Energy
Lattice Energy Application
Born Haber Cycle
Dipole Moment
Lewis Dot Structure
Octet Rule
Formal Charge
Resonance Structures
Additional Practice
Bond Energy

Resonance Strucutures are used to represent the different possible bonding arrangements in a molecule.

Examining Resonance Structures

Example #1: Determine all the possible Lewis structures possible for NO­2. Determine its resonance hybrid.

Many resonance structures involve the movement of a pi bond within a molecule. 

Example #2: Determine the remaining resonance structures possible for the following compound, CO­32-.

Additional Problems
In the resonance hybrid or experimentally determined structure of the nitrate ion (NO 3- ) it is observed that a. All the bonds are single bonds b. All the bonds are double bonds c. All the bonds have a bond order of 1.33 d. One bond is a double bond and the others are single bonds e. There are 23 valence electrons 
Which of the following is true? a. to convert from one resonance structure to another, only electrons can be moved b. to convert from one resonance structure to another, only atoms can be moved c. to convert from one resonance structure to another, electrons and atoms can both be moved d. to convert from one resonance structure to another, neither electrons nor atoms can be moved e. to convert from one resonance structure to another, electrons must always be added 
More than one Lewis formula resonance structure can be drawn for which of the following for minimum formal charge? 1. SbH3 2. SF4 3. CO2 4. H2O 5. O3
 For the molecule BF3, if we write the Lewis dot structure by first completing the octet around the pendant F atoms, we find that we have used all the valence electrons but the B has less than an octet (Structure A). Using our rules for drawing Lewis dot structures, we complete the octet around the B by forming double bonds from one of the F atoms which give rise to the resonance structures shown in Structure B. Structural characterization of BF3 suggests that there are no double bonds to F and that Structure A is the actual structure even though is does not obey the octet rule. In this case we can justify this structure based on Formal Charge arguments. Determine the formal charge on all the atoms in the electron deficient structure, Structure A, and on one of the resonance structures in Structure B and, using the rules of Formal Charge, tell why Structure A is the preferred one.
In which one of the following molecules is the best Lewis structure a resonance structure?  (a) CO2 (C = central atom) (b) ClO3− (Cl = central atom) (c) COCl2 (C = central atom) (d) NO2+ (N = central atom) (e) HCN (C = central atom)
Which of the following is the best resonance structure for the sulfite ion, SO 32–?
To convert from one resonance structure to another, _______. a) only atoms can be moved. b) electrons and atoms can be moved. c) neither atoms or electrons can be moved d) electrons must be added e) only electrons can be moved.
How many Lewis structures does CO32- have? A) 1 B) 2 C) 3 D) 4 E) 5
The electrons in the delocalized molecular orbitals of benzene (C6H6) a) are confined between two adjacent bonding atoms. b) are free to move around the six-membered ring. c) form the electron pairs in the C-H bonds of the compound. d) are unevenly distributed through the molecule. e) are responsible for the fact that the bonds between three pairs of carbon atoms in the ring are longer and stronger than the bonds between the other three pairs of carbon atoms. 
How many resonance structures are there for NO 3-? a) 1 b) 2 c) 3 d) 4 e) impossible to tell without more information
Consider the following Lewis structures of an organic compound with molecular formula C4H6O3. Note that all of the structures have the same number of electrons and atoms. 
Consider the following Lewis structures of an organic compound with molecular formula C4H6O3. Note that all of the structures have the same number of electrons and atoms.
The structure of the CO32– ion can be described in the Lewis formulation by these structures below. This means that  a) two carbon-to-oxygen bonds are single bonds; the third is a double bond. b) three independent forms of the CO32– ion coexist in equilibrium. c) the electrons must be rapidly exchanging among the three forms.  d) the CO32– ion exists in only one form: an average of the three principal structures shown.
Resonance structures describe molecules that have a) hybrid orbitals. b) rapid equilibria. c) resonating electrons.  d) multiple electron-dot formulas. 
Which dot structure is the best resonance structure for ICN? 
When a given molecule or ion is shown via resonance structures, the numerous structures 1. show the various stable isomers (or kinds) of a compound. 2. show the set of bonding extremes of which the average will better represent the actual bonding. 3. show how an isotope of one or more of the atoms is distributed within a molecule. 4. show the various possible geometries that a molecule or ion can assume. 5. show the nature of the various vibrations possible based on the nature of the kinds of atoms and bonds.
Which is true of the resonance structures of NO 2 shown below: a. Resonance structures only describe molecules that are uncharged. b. Only one of the resonance structures is actually correct c.The bond lengths of N-O bonds in NO 2 are equal d. Resonance structures have the same chemical formula but different arrangement of atoms in space. 
Two possible resonance structures for OCl2 are shown below. Which of the following is true? a. Neither structure is more accurate because they both have the same number of electrons b. Structure B is more accurate because it has more formal charge on the atoms c. The resonance structures are in equilibrium, rapidly switching back and forth d. Structure A is more accurate because the forma charge is 0 on each atom.
How many resonance structures are there for NO 3 – ? a. 1 b. 2 c. 3 d. 4 e. impossible to tell without more information
Draw the Lewis structure (including resonance structures) for the acetate ion (CH3COO-). For each resonance structure, assign formal charges to all atoms that have formal charge.
Each compound contains both ionic and covalent bonds.Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.BaCO3
Each compound contains both ionic and covalent bonds.Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.Ca(OH)2
Each compound contains both ionic and covalent bonds.Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.KNO3
Each compound contains both ionic and covalent bonds.Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.LiIO
Each compound contains both ionic and covalent bonds. Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.RbIO2
Each compound contains both ionic and covalent bonds. Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.NH4Cl
Each compound contains both ionic and covalent bonds. Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.KOH
Each compound contains both ionic and covalent bonds. Write ionic Lewis structures for each of them, including the covalent structure for the ion. Write resonance structures if necessary.Sr(CN)2
Draw a Lewis structure for nitric acid (the hydrogen atom is attached to one of the oxygen atoms). Include all three resonance hybrids by alternating the double bond among the three oxygen atoms.
Draw the Lewis structure for acetamide (CH3CONH2), an organic compound, and determine the geometry about each interior atom. Experiments show that the geometry about the nitrogen atom in acetamide is nearly planar. What resonance structure can account for the planar geometry about the nitrogen atom?Draw the Lewis structures for resonance forms of acetamide.
Ortho-dichlorobenzene, C6H4Cl2, is obtained when two of the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. Sketch the resonance structures for the molecule.
The organic molecules shown beloware derivatives of benzene in which additional six-membered rings are "fused" at the edges of the hexagons. The compounds are shown in the usual abbreviated method for organic molecules.Draw the additional resonance structure for naphthalene.
Barium azide is 62.04% Ba and 37.96% N. Each azide ion has a net charge of -1.Write three resonance structures for the azide ion.
Formic acid has the chemical formula HCOOH. It is a colorless liquid that has a density of 1.220 g/mL.The carbon atom in formic acid is bound to one H and both O’s. Draw the Lewis structure of the dominant resonance structure for formic acid.
Write the Lewis structure for each ion. Include resonance structures if necessary and assign formal charges to all atoms. If necessary, expand the octet on the central atom to lower formal charge.PO4 3 -
Consider the Lewis structure shown below. Are there multiple equivalent resonance structures for the species?
Benzene, an "aromatic" organic compound. The benzene molecule is a regular hexagon of carbon atoms with a hydrogen atom bonded to each one. The dashed lines represent the blending of two equivalent resonance structures, leading to C-C bonds that are intermediate between single and double bonds.What is the significance of the dashed bonds in this ball-and-stick model?
Molecular structure of ozone.What feature of this structure suggests that the two outer O atoms are in some way equivalent to each other?
The O-O bonds in ozone are often described as "one-and-a-half" bonds.Is this description consistent with the idea of resonance?
Do any of these resonance structures satisfy the octet rule for every atom in the molecule?
Do any of the four Lewis structures have multiple resonance structures?
Resonance. Describing a molecule as a blend of different resonance structures is similar to describing a paint color as a blend of primary colors. (a) Green paint is a blend of blue and yellow. We cannot describe green as a single primary color. (b) The ozone molecule is a blend of two resonance structures. We cannot describe the ozone molecule in terms of a single Lewis structure.Is the electron density consistent with equal weights for the two resonance structures for O3?
Ortho-dichlorobenzene, C6H4Cl2, is obtained when two of the adjacent hydrogen atoms in benzene are replaced with Cl atoms. A skeleton of the molecule is shown here. Are there any resonance structures for the molecule?
Suppose a particular AB3 molecule has the resonance structure Does this structure follow the octet rule?
The organic molecules shown beloware derivatives of benzene in which additional six-membered rings are "fused" at the edges of the hexagons. The compounds are shown in the usual abbreviated method for organic molecules.Would you expect naphthalene, anthracene, and tetracene to have multiple resonance structures?
What are resonance structures?
What is a resonance hybrid?
Do resonance structures always contribute equally to the overall structure of a molecule?
Each Lewis structure of benzene has three C=C double bonds. Another hydrocarbon containing three C=C double bonds is hexatriene , C6H8. A Lewis structure of hexatriene is Experiments show that three of the C-C bonds in hexatriene are shorter than the other two. Does this data suggest that hexatriene exhibits resonance structures?
How important is the resonance structure shown here to the overall structure of carbon dioxide?
Which of the molecules below will exhibit resonance?a. CO2b. CO32− c. NO3−d. O3
For the molecule COCl2 write the possible Lewis Dot structures and indicate the correct one based on formal charge arguments. Show the formal charges for all elements in each structure and indicate how you arrived at them. If any resonance structures are possible Lewis structures, then they should be indicated. 
Identify the major and minor resonance contributor(s) for the azide anion, N 3-.
Draw the Lewis structure for NO2 -  including any resonance structures. Which of the following statements is TRUE? a) The nitrite ion contains two N=O double bonds. b) There are no lone pairs of e - over the N atom. c) The ion contains one N-O bond and one N=O bond. d) The nitrite ion contains two N-O single bonds. e) The ion is nonpolar.
Draw the Lewis structures of the molecules below and use them to answer the following three questions.I. BH3II. NO2III. SF6IV. O3V. PF5a) How many of these molecules have no dipole moment?b) Which of these molecules show resonance?c) Which of these molecules obeys the octet rule?a) 1                 b) 2                 c) 3                 d) 4                 e) 5
BrO2- iona) Draw a valid alternative Lewis structure for this ion with one Br-O and one Br=O bondb) Determine the formal charge on each atom in the new structurec) Based on the formal charges you determine which is the best structure and what criteria are used with formal charge to determine the best structure?
Consider the following pairs A and B of Lewis structures. Select the one from each pair that is likely to make the dominant contribution to a resonance hybrid.  1. A1 and B2 2. A2 and B1 3. A1 and B1 4. A2 and B2
Draw four possible Lewis structures of the molecule xenon trioxide, XeO 3, one each with zero, one, two, or three Xe−O double bonds. Include all lone pairs of electrons. Show the formal charges of all atoms in the structures.     Do any of these resonance structures satisfy the octet rule for every atom in the molecule?A. Yes, the structure with two double bonds obeys the octet rule for all atoms.B. Yes, the structure with no double bonds obeys the octet rule for all atoms.C. Yes, the structure with three double bonds obeys the octet rule for all atoms.D. Yes, the structure with one double bonds obeys the octet rule for all atoms. Do any of the four Lewis structures have multiple resonance structures? Check all that apply.A. The structure with one double bond.B. The structure with no double bonds.C. The structure with three double bond.D. The structure with two double bonds Which of the Lewis structures for XeO 3 yields the most favorable formal charges for the molecule?A. The structure with 1 double bonds minimizes formal charges on all atoms.B. The structure with 3 double bonds minimizes formal charges on all atoms.C. The structure with no double bonds minimizes formal charges on all atoms.D. The structure with 2 double bonds minimizes formal charges on all atoms.
Draw all of the Lewis structures of NO 2+ which obey the octet rule and use this Lewis structure or these resonance structures to predict how many covalent bonds connect each oxygen atom in the real structure to the central N atom. Assume that the octet rule is followed for the N atom when you draw your structure(s). Pick the correct statement from the choices below. a) Each oxygen atom is connected to the central N atom with 2 covalent bonds. b) Each oxygen atom is connected to the central N atom with 1 covalent bonds. c) Each oxygen atom is connected to the central N atom with 1.33 covalent bonds. d) Each oxygen atom is connected to the central N atom with 1.25 covalent bonds. e) Each oxygen atom is connected to the central N atom with 1.5 covalent bonds.
Which one of the following is expected to exhibit resonance? A) CO2 B) NO2- C) NH4+ D) HCN
How many resonance structures can be drawn for ozone O3?