Structure and Bonding

While the most common isotope of nitrogen has a mass number of 14 (nitrogen-14), a radioactive isotope of nitrogen has a mass number of 13 (nitrogen-13). Nitrogen-13 is used in PET (positron emission tomography) scans by physicians to monitor brain activity and diagnose dementia. For each isotope, give the following information: (a) the number of protons; (b) the number of neutrons; (c) the number of electrons in the neutral atom; (d) the group number; and (e) the number of valence electrons.

Question: While the most common isotope of nitrogen has a mass number of 14 (nitrogen-14), a radioactive isotope of nitrogen has a mass number of 13 (nitrogen-13). Nitrogen-13 is used in PET (positron emission tomography) scans by physicians to monitor brain activity and diagnose dementia. For each isotope, give the following information: (a) the number of protons; (b) the number of neutrons; (c) the number of electrons in the neutral atom; (d) the group number; and (e) the number of valence electrons.

Question: Label each bond in the following compounds as ionic or covalent.

$$\begin{gathered} a\mathit{.}\mathit{ }{F}_{\mathit{2}} \\ b\mathit{.}\mathit{ }LiBr \\ c\mathit{.}\mathit{ }C{H}_{\mathit{3}}C{H}_{\mathit{3}} \\ d\mathit{.}\mathit{ }NaN{H}_{\mathit{2}} \\ e\mathit{.}\mathit{ }NaOC{H}_{\mathit{2}} \end{gathered}$$

Question: How many covalent bonds are predicted for each atom? 

$a\mathit{.}\mathit{ }O\mathit{ }b\mathit{.}\mathit{ }Al\mathit{ }c\mathit{.}\mathit{ }Br\mathit{ }d\mathit{.}\mathit{ }Si$

Question: Draw a valid Lewis structure for each species.

$a\mathit{.}\mathit{ }C{H}_{\mathit{3}}C{H}_{\mathit{3}\mathit{ }\mathit{ }\mathit{ }\mathit{ }\mathit{ }\mathit{ }}b\mathit{.}\mathit{ }C{H}_{\mathit{5}}N\mathit{ }\mathit{ }\mathit{ }c\mathit{.}\mathit{ }C{H}_{\mathit{3}}Cl$

Question: Draw an acceptable Lewis structure for each compound, assuming the atoms are connected as arranged. Hydrogen cyanide$\left(\mathrm{HCN}\right)$is a poison, formaldehyde $\left({\mathrm{H}}_2\mathrm{CO}\right)$ is a preservative, and glycolic acid $\left({\mathrm{OHCH}}_2{\mathrm{CO}}_2\mathrm{H}\right)$is used to make dissolving sutures.

$\begin{array}{rcl}& & \mathrm{a}. \mathrm{HCN} \mathrm{H} \mathrm{C} \mathrm{N} \mathrm{b}. {\mathrm{HC}}_2\mathrm{O} \end{array}$ $\begin{array}{rcl}& & \mathrm{H} \mathrm{C} \mathrm{O} \\ & & \mathrm{H}\end{array}$$\mathrm{c}. {\mathrm{OHCH}}_2{\mathrm{CO}}_{2}H$$$\begin{gathered} \mathrm{OH} \\ \mathrm{HOCCOH} \\ \mathrm{H} \end{gathered}$$

Question: Draw a Lewis structure for each ion.

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}{\mathbf{O}}^{\mathbf{-}} \\ \mathbf{b}\mathbf{.}\mathbf{ }{{\mathbf{HC}}_{\mathbf{2}}}^{\mathbf{-}} \\ \mathbf{c}\mathbf{.}\mathbf{ }{\left({\mathrm{CH}}_3{\mathrm{NH}}_3\right)}^{\mathbf{+}} \\ \mathbf{d}\mathbf{.}\mathbf{ }{\left({\mathrm{CH}}_3\mathrm{NH}\right)}^{-} \end{gathered}$$

Question: What is the formal charge on the O atom in each of the following species that contains a multiple bond to O?

a.

b.

c.  

Question: Draw Lewis structures for each molecular formula.

a. C₂H₄Cl₂ ( two isomers)

b. C₃H₈O  (three isomers) 

c. C₃H₆   (two isomers)

Question: Classify each pair of compounds as isomers or resonance structures

a.

b.

Question: Considering structures, A–D, classify each pair of compounds as isomers, resonance structures, or neither: (a) A and B; (b) A and C; (c) A and D; (d) B and D.

Question: Follow the curved arrows to draw a second resonance structure for each species.

                                              a.

                                   b. 

Question: Use curved arrow notation to show how the first resonance structure can be converted to the second.

a.

b.

Question: Draw a second resonance structure for each species in parts (a) and (b). Draw two additional resonance structures for the ion in part (c).

a.

b.

c. 

Question: Label the resonance structures in each pair as major, minor, or equal contributors to the hybrid. Then draw the hybrid.

a.

b. 

Question: (a) Draw a second resonance structure for A. (b) Why can’t a second resonance

 structure be drawn for B?

Question: Predict the indicated bond angles in each compound drawn as a Lewis structure with no implied geometry.

                                    a.

                                     b.

                                      c.  

Question: Determine the geometry around all second-row elements in each compound drawn as a Lewis structure with no implied geometry.

                                                a.

                                               b.

                                                  c.  

                                               d.  

Question: Convert each condensed formula to a Lewis structure

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}{\left({\mathrm{CH}}_2\right)}_{\mathbf{4}}\mathbf{CH}{\left({\mathrm{CH}}_3\right)}_{\mathbf{2}} \\ \mathbf{b}\mathbf{.}\mathbf{ }{\left({\mathrm{CH}}_3\right)}_{\mathbf{3}}\mathbf{CCH}\left(\mathrm{OH}\right){\mathbf{CH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}} \\ \mathbf{c}\mathbf{.}\mathbf{ }{\left({\mathrm{CH}}_3\right)}_{\mathbf{2}}\mathbf{CHCHO} \\ \mathbf{d}\mathbf{.}\mathbf{ }{\left({\mathrm{OHCH}}_2\right)}_{\mathbf{2}}\mathbf{CH}{\left({\mathrm{CH}}_2\right)}_{\mathbf{3}}\mathbf{C}{\left({\mathrm{CH}}_3\right)}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}} \end{gathered}$$

Question: During periods of strenuous exercise, the buildup of lactic acid $\left[{\mathrm{CH}}_3\mathrm{CH}\left(\mathrm{OH}\right){\mathrm{CO}}_{2}H\right]$ causes the aching feeling in sore muscles. Convert this condensed structure to a Lewis structure of lactic acid.

Question: How many hydrogen atoms are present around each highlighted carbon atom in the following molecules? What is the molecular formula for each molecule? Both compounds are active ingredients in some common sunscreens.

Question: Convert each skeletal structure to a complete structure with all C’s, H’s, and lone pairs drawn in.   

                                                        a.

                                                        b.

                                                c.

                                               d. 

Question: Draw in all hydrogens and lone pairs on the charged carbons in each ion.

                                                a.

                                              b.

                                    c.

                                          d. 

Question: Draw a skeletal structure for the molecules in parts (a) and (b), and a condensed structure for the molecules in parts (c) and (d).

                                   a.

                                      b.

                                        c.

                                        d. 

Question: What orbitals are used to form each of the C-C and C-H bonds in ${\mathbf{CH}}_{\mathbf{3}}{\mathbf{CH}}_{\mathbf{2}}{\mathbf{CH}}_{\mathbf{3}}$ (propane)? How many bonds are present in this molecule?

Question: What orbitals are used to form each bond in the following molecules?

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}\mathbf{BeH} \\ \mathbf{b}\mathbf{.}{\left({\mathrm{CH}}_3\right)}_{\mathbf{3}}\mathbf{B} \\ \mathbf{c}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}{\mathbf{OCH}}_{\mathbf{3}} \end{gathered}$$

Question: Determine the hybridization around the highlighted atoms in each molecule.

                                           a.

                                           b.

                                            c. 

Question: The unmistakable odor of a freshly cut cucumber is largely due to cucumber aldehyde. (a) How many ${\mathbf{sp}}^{\mathbf{2}}$ hybridized carbon atoms does cucumber aldehyde contain? (b) What is the hybridization of the O atom? (c) What orbitals are used to form the carbon-oxygen double bond? (d) How many $\mathbf{\sigma }$ bonds does cucumber aldehyde contain? (e) How many   bonds does it contain?

Question: Which of the bond shown in red in each compound or pair of compounds is shorter?

                               a.

                               b.

                               c.

                                 d. 

Question: Rank the following atoms in order of increasing electronegativity. Label the most electronegative and most electropositive atom in each group.

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }\mathbf{Se}\mathbf{,}\mathbf{O}\mathbf{,}\mathbf{S} \\ \mathbf{b}\mathbf{.}\mathbf{ }\mathbf{P}\mathbf{,}\mathbf{Na}\mathbf{,}\mathbf{Cl} \\ \mathbf{c}\mathbf{.}\mathbf{ }\mathbf{Cl}\mathbf{,}\mathbf{S}\mathbf{,}\mathbf{F} \\ \mathbf{d}\mathbf{.}\mathbf{ }\mathbf{O}\mathbf{,}\mathbf{P}\mathbf{,}\mathbf{N} \end{gathered}$$

Question: Show the direction of the dipole in each bond. Label the atoms with ${\mathbf{CH}}_{\mathbf{3}}\mathbf{Br}\mathbf{ }\mathbf{and}\mathbf{ }{\mathbf{\delta }}^{\mathbf{-}}$.

                                       a.

                                        b.

                                       c.

                                      d.   

Question: Indicate which of the following molecules is polar because it possesses a net dipole. Show the direction of the net dipole if one exists. 

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{3}}\mathbf{Br} \\ \mathbf{b}\mathbf{.}\mathbf{ }{\mathbf{CH}}_{\mathbf{2}}{\mathbf{Br}}_{\mathbf{2}} \\ \mathbf{c}\mathbf{.}\mathbf{ }{\mathbf{CF}}_{\mathbf{4}} \end{gathered}$$

d.

e.

Question: Provide the following information about L-dopa. 

a. Label all ${\mathbf{sp}}^{\mathbf{3}}$ hybridized C atoms.

b. Label all H atoms that bear a partial positive charge$\left({\delta }^{+}\right)$.

 c. Draw another resonance structure.

Question: Use the ball-and-stick model to answer each question about carbidopa, a drug used in combination with l-dopa to treat Parkinson’s disease. 

a. Draw a skeletal structure of carbidopa

b. Determine the hybridization around each carbon atom.

c.  What is the hybridization and geometry around each N atom? 

d. How many polar bonds are present?

Question: Citric acid is responsible for the tartness of citrus fruits, especially lemons and limes.

a. What is the molecular formula for citric acid?

b. How many lone pairs are present?

c. Draw a skeletal structure. 

d. How many ${\mathrm{sp}}^2$hybridized carbons are present?

e. What orbitals are used to form each indicated bond ([1]–[4])?

Question: Zingerone gives ginger its pungent taste.

a. What is the molecular formula for zingerone?  

b. How many lone pairs are present?

c. Draw a skeletal structure. 

d. How many ${\mathrm{sp}}^2$ hybridized carbons are present? 

e. What orbitals are used to form each indicated bond ([1]–[4])?  

Question: Assign formal charges to each carbon atom in the given species. All lone pairs have been drawn in.

a.

b.

c.

d.

Question: Assign formal charges to each N and O atom in the given molecules. All lone pairs have been drawn in.

                                             a.

                                              b.

                                               c.

                                               d.

Question: Draw an acceptable Lewis structure from each condensed structure, such that all atoms have zero formal charges.

1. Diethyl ether, ${\left({\mathrm{CH}}_3{\mathrm{CH}}_2\right)}_{\mathbf{2}}\mathbf{O}$the first general anesthetic used in medical procedures
2. Acrylonitrile, ${\mathbf{CH}}_{\mathbf{2}}\mathbf{CHCN}$starting material used to manufacture synthetic Orlon fibers
3. Dihydroxyacetone, ${\left({\mathrm{HOCH}}_2\right)}_{\mathbf{2}}\mathbf{CO}$ , an ingredient in sunless tanning products
4. Acetic anhydride,  ${\left({\mathrm{CH}}_3\mathrm{CO}\right)}_{\mathbf{2}}\mathbf{CO}$a reagent used to synthesize aspirin

Question: Creatine is a dietary supplement used by some athletes to boost their athletic performance.

(a) Draw in all lone pairs in creatine. (b) Draw two additional resonance structures showing all lone pairs and formal charges.

Question: Draw Lewis structures for the nine isomers having a molecular formula${\mathbf{C}}_{\mathbf{3}}{\mathbf{H}}_{\mathbf{6}}\mathbf{O}$ , with all atoms having a zero formal charge.

Question: With reference to compound A drawn below, label each compound as an isomer, a resonance structure, or neither.

Question: With reference to cation B, label each species as an isomer, a resonance structure, or neither

Question: How are the molecules or ions in each pair related? Classify them as resonance structures, isomers, or neither.

                                 a.   and

                                 b.  and 

                                 c. and 

                                  d.    and 

Question: Add curved arrows to show how the first resonance structure can be converted into the second.

                            a.

                          b.

Question: Draw a second resonance structure for each ion. Then, draw the resonance hybrid.

                                      a.

                                         b.

                                       c.

Question: Draw all reasonable resonance structures for each species.

$$\begin{gathered} \mathbf{a}\mathbf{.}\mathbf{ }{{\mathbf{O}}_{\mathbf{3}}}^{\mathbf{-}} \\ \mathbf{b}\mathbf{.}\mathbf{ }{{\mathbf{NO}}_{\mathbf{3}}}^{\mathbf{-}}\mathbf{(}\mathbf{a}\mathbf{ }\mathbf{central}\mathbf{ }\mathbf{N}\mathbf{ }\mathbf{atom}\mathbf{)} \\ \mathbf{c}\mathbf{.}\mathbf{ }{{\mathbf{N}}_{\mathbf{3}}}^{\mathbf{-}} \end{gathered}$$

d.

e. 

Question: Consider compounds A–D, which contain both a heteroatom and a double bond. (a) For which of the compounds are no additional Lewis structures possible? (b) When two or more Lewis structures can be drawn, draw all additional resonance structures.

Question: Draw four additional resonance structures for the following cation. Then draw the resonance hybrid.