Resonance Structures

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

Examining Resonance Structures

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

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

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

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Resonance Structures Additional Practice Problems

Which of the molecules below will exhibit resonance?

a. CO2

b. CO32− 

c. NO3

d. O3

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Draw a Lewis structure for SO2 in which all atoms obey the octet rule. Show formal charges.

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-What are the formal charges on the sulfur (S), carbon (C), and nitrogen (N) atoms, respectively, in the resonance structure that contributes most to the stability of the thiocyanate ion, SCN - ??

The possible resonance structures for the thiocyanate ion, SCN -?

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Identify the major and minor resonance contributor(s) for the azide anion, N 3-.

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Draw the Lewis structure for the trisulfur (S 3) molecule. Be sure to include all resonance structures that satisfy the octet rule.

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Draw and name all possible constitutional isomers of alcohols with the molecular formula C4H10O.

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Draw a Lewis structure for the molecule SCN - with C as the central atom, including formal charges and resonance structures (you should have three structures)

Do the same with N as the central atom (again, you should have three structures) Based on the formal charges, which order (SCN- or SNC-) represents the more stable structure? For the more stable order (SCN- or SNC-) which of the three resonance structures you drew is the "best" structure according to the rules of Lewis dot structures and formal charges? Explain your answers.

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Draw the Lewis structures for three resonance forms of nitrate, NO 3-. Include electron lone pairs, and any formal charges.

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A single Lewis Structure of the formate ion (HCO 2-) is shown below. Which statement best describes the bonding character of this ion?

(a) One double bond and two single bonds

(b) One double bond and two delocalized single bonds

(c) Three equivalent 1 1/3 bonds

(d) One single bond and two equivalent 1 1/2 bonds

(e) 007 James Bonds

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The formate ion, HCO2-, is formed when formic acid dissolves in water. A number of possible resonance structures for this ion are shown. Which of these structures are valid and which are invalid? Drag each item to the appropriate bin.

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Draw the Lewis structure of the carbonate ion (CO 32-) showing all possible resonance structures if there are any. Determine the formal charge of each atom.

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Draw the Lewis structure for the disulfur monoxide (S 2O) molecule. Be sure to include all resonance structures that satisfy the octet rule.

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Draw out the Lewis structures for H 2CO3, HCO3-, and CO32-. Then determine the maximum number of equivalent resonance structures for each species. Note that carbon is the central atom in all three cases. If the molecule contains hydrogen atoms they are attached to oxygen atoms. Only count the best structures. For example, a structure with really bad formal charges should not be counted.

The molecule H2CO3 has______ equivalent Lewis structures.
The molecule HCO3- has______ equivalent Lewis structures.
The molecule CO32- has______ equivalent Lewis structures

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Select the true statements regarding these resonance structures of formate.

A. The actual structure of formate is an average of the two resonance forms.

B. Each carbon-oxygen bond is somewhere between a single and double bond.

C.The actual structure of formate switches back and forth between the two resonance forms.

D. Each oxygen atom has a double bond 50% of the time.

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How many resonance structures can be drawn for ozone O3?

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Draw the lewis structures (resonance) of NH 2-

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A Lewis structure for the carbonate ion (CO32-) is drawn below, but incomplete. Complete the structure by adding in formal charges and non-bonding electrons. Then draw the other two major resonance structures that fit the octet rule.

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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.

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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.

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BrO2- ion

a) Draw a valid alternative Lewis structure for this ion with one Br-O and one Br=O bond

b) Determine the formal charge on each atom in the new structure

c) 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?

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Draw the Lewis structure of bicarbonate (HCO 3-) showing all possible resonance structures if there are any. Determine the formal charge of each atom.

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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. Include all hydrogen atoms and nonbonding electrons.

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Draw the Lewis structure for NO3- (the nitrate ion). Include formal charges and resonance structures as needed.

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Draw the Lewis structures for BrO3-  and indicate the formal charges for Br and O’s.

a) Indicate the total number of valence electrons

b) Describe the preferred Lewis structure.

c) How many resonance structures are there in the ion?

d) Give the name of the ion.

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Draw Lewis structure(s) for the nitronium ion ( NO 2+ ).

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Show resonance structures for acetate ion (CH 3CO2-)

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How many Lewis structures does CO32- have?

A) 1

B) 2

C) 3

D) 4

E) 5

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Draw the Lewis electron dot diagrams for the following chemical species and include all reasonable resonance diagrams, if any. Hint: Minimize formal charge without breaking the Octet rule unless the atom is in period 3 or higher.

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Draw the Lewis electron dot diagrams for the following chemical species and include all reasonable resonance diagrams, if any. Hint: Minimize formal charge without breaking the Octet rule unless the atom is in period 3 or higher.

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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.

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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

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When drawing the Lewis structure for SO2 where all formal charges equal zero, which answer describes the sulfur (S) atom:

A. Two single bonds and two lone pairs

B. One double bond, one single bond and one lone pair

C. Two double bonds and one lone pair

D. One double bond, one single bond and two lone pairs

E. Two single bonds and three lone pairs

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Which one of the following is expected to exhibit resonance?

A) CO2

B) NO2-

C) NH4+

D) HCN

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Resonance structures describe molecules that have

a) hybrid orbitals.

b) rapid equilibria.

c) resonating electrons. 

d) multiple electron-dot formulas. 

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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.

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Which dot structure is the best resonance structure for ICN? 

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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)

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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. 

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Which of the following is the best resonance structure for the sulfite ion, SO 32–?

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Draw the Lewis structures of the molecules below and use them to answer the following three questions.

I. BH3

II. NO2

III. SF6

IV. O3

V. PF5

a) 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

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Draw the Lewis structure for NO-  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.

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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.

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How many resonance structures are there for NO 3-?

a) 1

b) 2

c) 3

d) 4

e) impossible to tell without more information

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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

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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 

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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 

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How many resonance structures are there for NO 3 ?

a. 1

b. 2

c. 3

d. 4

e. impossible to tell without more information

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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.

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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. 

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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.

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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. 

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