Chapter 9

Give the periodic group number and number of valence electrons for each of the following atoms. (a) \(\mathrm{O}\) (d) \(\mathrm{Mg}\) (b) \(B\) (e) \(\mathrm{F}\) (c) \(\mathrm{Na}\) (f) \(\mathrm{S}\)

Give the periodic group number and number of valence electrons for each of the following atoms. (a) \(\mathrm{C}\) (d) Si (b) \(\mathrm{Cl}\) (e) Se (c) \(\mathrm{Ne}\) (f) \(\mathrm{Al}\)

For elements in Groups \(3 \mathrm{A}-7 \mathrm{A}\) of the periodic table, give the number of bonds an element is expected to form if it obeys the octet rule.

Which of the following elements are capable of forming compounds in which the indicated atom has more than four valence electron pairs? (a) C (b) P (c) O (d) F (c) Cl (f) B (g) Se (h) \(\mathrm{Sn}\)

Which of the following ionic compounds are not likely to exist: \(\mathrm{MgCl}, \mathrm{ScCl}_{3}, \mathrm{BaF}_{3}, \mathrm{CsKr}, \mathrm{Na}_{2} \mathrm{O} ?\) Explain your choices.

List the following compounds in order of increasing lattice energy (from least negative to most negative): LiI, LiF, \(\mathrm{CaO}, \mathrm{RbI}\).

To melt an ionic solid, energy must be supplied to disrupt the forces between ions so the regular array of ions collapses. If the distance between the anion and the cation in a crystalline solid decreases (but ion charges remain the same), should the melting point decrease or increase? Explain.

Which compound in each of the following pairs should require the higher temperature to melt? (See Study Question \(9 .)\) (a) NaCl or RbCl (b) \(\mathrm{BaO}\) or \(\mathrm{MgO}\) (c) \(\mathrm{NaCl}\) or \(\mathrm{MgS}\)

Draw a Lewis structure for each of the following molecules or ions. (a) \(\mathrm{NF}_{3}\) (b) \(\mathrm{ClO}_{3}^{-}\) (c) HOBr (d) \(\mathrm{SO}_{3}^{2-}\)

Draw a Lewis structure for each of the following molecules or ions: (a) \(\mathrm{CS}_{2}\) (b) \(\mathrm{BF}_{4}^{-}\) (c) \(\mathrm{NO}_{2}^{-}\) (d) \(\mathrm{SOCl}_{2}\)

Draw a Lewis structure for each of the following molecules. (a) Methanol, \(\mathrm{CH}_{3} \mathrm{OH}\) (C is the central atom) (b) Vinyl chloride, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCl}\), the molecule from which PVC plastics are made. (c) Acrylonitrile, \(\mathrm{H}_{2} \mathrm{C}=\mathrm{CHCN}\), the molecule from which materials such as Orlon are made. (EQUATION CAN'T COPY)

Show all possible resonance structures for each of the following molecules or ions. (a) \(\mathrm{SO}_{2}\) (b) \(\mathrm{NO}_{2}^{-}\) (c) \(\mathrm{SCN}^{-}\)

Show all possible resonance structures for each of the following molecules or ions: (a) Nitrate ion, \(\mathrm{NO}_{3}^{-}\) (b) Nitric acid, HNO \(_{3}\) (c) Nitrous oxide (laughing gas), \(\mathrm{N}_{2} \mathrm{O}\)

Draw a Lewis structure for each of the following molecules or ions. (a) \(\mathrm{BrF}_{3}\) (b) \(\mathrm{I}_{3}^{-}\) (c) \(\mathrm{XeO}_{2} \mathrm{F}_{2}\) (d) \(\mathrm{XeF}_{3}^{+}\)

Draw a Lewis structure for each of the following molecules or ions: (a) \(\mathrm{BrF}_{5}\) (b) IF \(_{3}\) (c) \(\mathrm{IBr}_{2}^{-}\) (d) \(\mathrm{BrF}_{2}^{+}\)

Draw a Lewis structure for each of the following molecules or ions. Describe the electron-pair geometry and the molecular geometry around the central atom. (a) \(\mathrm{NH}_{2} \mathrm{Cl}\) (b) \(\mathrm{Cl}_{2} \mathrm{O}\) (O is the central atom) (c) \(\mathrm{SCN}^{-}\) (d) HOF

Draw a Lewis structure for each of the following molecules or ions. Describe the electron-pair geometry and the molecular geometry around the central atom. (a) \(\mathrm{ClF}_{2}^{+}\) (b) \(\mathrm{SnCl}_{3}^{-}\) (c) \(\mathrm{PO}_{4}^{3-}\) (d) \(\mathrm{CS}_{2}\)

The following molecules or ions all have two oxygen atoms attached to a central atom. Draw a Lewis structure for each one and then describe the electron-pair geometry and the molecular geometry around the central atom. Comment on similarities and differences in the series. (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{NO}_{2}^{-}\) (c) \(\mathrm{O}_{3}\) (d) \(\mathrm{ClO}_{2}^{-}\)

The following molecules or ions all have three oxygen atoms attached to a central atom. Draw a Lewis structure for each one and then describe the electron-pair geometry and the molecular geometry around the central atom. Comment on similarities and differences in the series. (a) \(\mathrm{CO}_{3}^{2-}\) (b) \(\mathrm{NO}_{3}^{-}\) (c) \(\mathrm{SO}_{3}^{2-}\) (d) \(\mathrm{ClO}_{3}^{-}\)

Draw a Lewis structure for each of the following molecules or ions. Describe the electron-pair geometry and the molecular geometry around the central atom. (a) \(\mathrm{ClF}_{2}^{-}\) (b) \(\mathrm{ClF}_{3}\) (c) \(\mathrm{CIF}_{4}^{-}\) (d) CIF \(_{5}\)

Draw a Lewis structure of each of the following molecules or ions. Describe the electron-pair geometry and the molecular geometry around the central atom. (a) \(\mathrm{SiF}_{6}^{2-}\) (b) \(\mathrm{PF}_{5}\) (c) \(\mathrm{SF}_{4}\) (d) \(\mathrm{XeF}_{4}\)

Give approximate values for the indicated bond angles. (a) \(\mathrm{O}-\mathrm{S}-\mathrm{O}\) in \(\mathrm{SO}_{2}\) (b) \(\mathrm{F}-\mathrm{B}-\mathrm{F}\) angle in \(\mathrm{BF}_{3}\) (c) \(\mathrm{Cl}-\mathrm{C}-\mathrm{Cl}\) angle in \(\mathrm{Cl}_{2} \mathrm{CO}\) (c) \(\mathrm{H}-\mathrm{C}-\mathrm{H}\) (angle 1 ) and \(\mathrm{C}-\mathrm{C} \equiv \mathrm{N}\) (angle 2 ) in acetonitrile. (EQUATION CAN'T COPY)

Determine the formal charge on each atom in the following molecules or ions: (a) \(\mathrm{N}_{2} \mathrm{H}_{4}\) (c) \(\mathrm{BH}_{4}^{-}\) (b) \(\mathrm{PO}_{4}^{3-}\) (d) \(\mathrm{NH}_{2} \mathrm{OH}\)

Determine the formal charge on each atom in the following molecules or ions. (a) SCO (b) \(\mathrm{HCO}_{2}^{-}\) (formate ion) (c) \(\mathbf{O}_{3}\) (d) \(\mathrm{HCO}_{2} \mathrm{H}\) (formic acid)

Determine the formal charge on each atom in the following molecules and ions. (a) \(\mathrm{NO}_{2}^{+}\) (c) \(\mathrm{NF}_{3}\) (b) \(\mathrm{NO}_{2}^{-}\) (d) HNO \(_{3}\)

Determine the formal charge on each atom in the following molecules and ions. (a) \(\mathrm{SO}_{2}\) (c) \(\mathrm{SO}_{2} \mathrm{Cl}_{2}\) (b) \(\mathrm{SOCl}_{2}\) (d) \(\mathrm{FSO}_{3}^{-}\)

For each pair of bonds, indicate the more polar bond and use an arrow to show the direction of polarity in each bond. (a) \(\mathrm{C}-\mathrm{O}\) and \(\mathrm{C}-\mathrm{N}\) (c) \(\mathrm{B}-\mathrm{O}\) and \(\mathrm{B}-\mathrm{S}\) (b) \(\mathrm{P}-\mathrm{Br}\) and \(\mathrm{P}-\mathrm{Cl}\) (d) \(\mathrm{B}-\mathrm{F}\) and \(\mathrm{B}-\mathrm{I}\)

For each of the bonds listed below, tell which atom is the more negatively charged. (a) \(\mathrm{C}-\mathrm{N}\) (c) \(\mathrm{C}-\mathrm{Br}\) (b) \(\mathrm{C}-\mathrm{H}\) (d) \(\mathrm{S}-\mathrm{O}\)

Acrolein, \(C_{3} H_{4} O,\) is the starting material for certain plastics. (EQUATION CAN'T COPY) (a) Which bonds in the molecule are polar and which are nonpolar? (b) Which is the most polar bond in the molecule? Which is the more negative atom of this bond?

Considering both formal charges and bond polarities, predict on which atom or atoms the negative charge resides in the following anions: (a) \(\mathrm{OH}^{-}\) (b) \(\mathrm{BH}_{4}^{-}\) (c) \(\mathrm{CH}_{3} \mathrm{CO}_{2}^{-}\)

Considering both formal charge and bond polarities, predict on which atom or atoms the positive charge resides in the following cations. (a) \(\mathrm{H}_{3} \mathrm{O}^{+}\) (c) \(\mathrm{NO}_{2}^{+}\) (b) \(\mathrm{NH}_{4}^{+}\) (d) \(\mathrm{NF}_{4}^{+}\)

Three resonance structures are possible for dinitrogen oxide, \(\mathrm{N}_{2} \mathrm{O}\) (a) Draw the three resonance structures. (b) Calculate the formal charge on each atom in each resonance structure. (c) Based on formal charges and electro negativity, predict which resonance structure is the most reasonable.

Compare the electron dot structures of the carbonate \(\left(\mathrm{CO}_{3}^{2-}\right)\) and borate \(\left(\mathrm{BO}_{3}^{3-}\right)\) ions. (a) Are these ions isoelectronic? (b) How many resonance structures does each ion have? (c) What are the formal charges of each atom in these ions? (d) If an \(\mathrm{H}^{+}\) ion attaches to \(\mathrm{CO}_{3}^{2-}\) to form the bicarbonate ion, \(\mathrm{HCO}_{3}^{-},\) does it attach to an \(\mathrm{O}\) atom or to the Catom?

Two resonance structures are possible for \(\mathrm{NO}_{2}^{-} .\) Draw these structures and then find the formal charge on each atom in each resonance structure. If an \(\mathrm{H}^{+}\) ion is attached to \(\mathrm{NO}_{2}^{-}\) (to form the acid \(\mathrm{HNO}_{2}\) ), does it attach to \(\mathrm{O}\) or N?

Draw the resonance structures for the formate ion, \(\mathrm{HCO}_{2}^{-}\) and find the formal charge on each atom. If an \(\mathrm{H}^{+}\) ion is attached to \(\mathrm{HCO}_{2}^{-}\) (to form formic acid), does it attach to Cor O?

Consider the following molecules: (a) \(\mathrm{H}_{2} \mathrm{O}\) (c) \(\mathrm{CO}_{2}\) (e) \(\mathrm{CCl}_{4}\) (b) \(\mathrm{NH}_{3}\) (d) CIF (i) In which compound are the bonds most polar? (ii) Which compounds in the list are not polar? (iii) Which atom in CIF is more negatively charged?

Consider the following molecules: (a) \(\mathrm{CH}_{4}\) (c) \(\mathrm{BF}_{3}\) (b) \(\mathrm{NH}_{2} \mathrm{Cl}\) (d) \(\mathrm{CS}_{2}\) (i) Which compound has the most polar bonds? (ii) Which compounds in the list are not polar?

Which of the following molecules is (are) polar? For each polar molecule, indicate the direction of polarity-that is, which is the negative end and which is the positive end of the molecule. (a) \(\mathrm{BeCl}_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{Cl}\) (b) \(\mathrm{HBF}_{2}\) (d) \(\mathrm{SO}_{3}\)

Which of the following molecules is (are) not polar? Which molecule has the most polar bonds? (a) CO (d) \(\mathrm{PCl}_{3}\) (b) \(\mathrm{BCl}_{3}\) (e) \(\mathrm{GeH}_{4}\) (c) \(\mathrm{CF}_{4}\)

Give the bond order for each bond in the following molecules or ions. (a) \(\mathrm{CH}_{2} \mathrm{O}\) (c) \(\mathrm{NO}_{2}^{+}\) (b) \(\mathrm{SO}_{3}^{2-}\) (d) NOCl

Give the bond order for each bond in the following molecules or ions. (a) \(\mathrm{CN}^{-}\) (b) \(\mathrm{CH}_{3} \mathrm{CN}\) (c) \(\mathrm{SO}_{3}\) (d) \(\mathrm{CH}_{3} \mathrm{CH}=\mathrm{CH}_{2}\)

In each pair of bonds, predict which is shorter. (a) \(\mathrm{B}-\mathrm{Cl}\) or \(\mathrm{Ga}-\mathrm{Cl}\) (b) \(\mathrm{Sn}-\) O or \(\mathrm{C}-\mathrm{O}\) (c) \(\mathrm{P}-\mathrm{S}\) or \(\mathrm{P}-\mathrm{O}\) (d) \(\mathrm{C}=\mathrm{O}\) or \(\mathrm{C}=\mathrm{N}\)

In each pair of bonds, predict which is shorter. (a) \(\mathrm{Si}-\mathrm{N}\) or \(\mathrm{Si}-\mathrm{O}\) (b) \(\mathrm{Si}-\mathrm{O}\) or \(\mathrm{C}-\mathrm{O}\) (c) \(\mathrm{C}-\mathrm{F}\) or \(\mathrm{C}-\mathrm{Br}\) (d) The \(\mathrm{C}-\mathrm{N}\) bond or the \(\mathrm{C} \equiv \mathrm{N}\) bond in \(\mathrm{H}_{2} \mathrm{NCH}_{2} \mathrm{C} \equiv \mathrm{N}\)

Consider the nitrogen-oxygen bond lengths in \(\mathrm{NO}_{2}^{+}\) \(\mathrm{NO}_{2}^{-},\) and \(\mathrm{NO}_{3}^{-} .\) In which ion is the bond predicted to be longest? In which is it predicted to be the shortest? Explain briefly.

Compare the carbon-oxygen bond lengths in the formate ion \(\left(\mathrm{HCO}_{2}^{-}\right),\) in methanol \(\left(\mathrm{CH}_{3} \mathrm{OH}\right),\) and in the carbonate ion \(\left(\mathrm{CO}_{3}^{2-}\right) .\) In which species is the carbon-oxygen bond predicted to be longest? In which is it predicted to be shortest? Explain briefly.

Consider the carbon-oxygen bond in formaldehyde \(\left(\mathrm{CH}_{2} \mathrm{O}\right)\) and carbon monoxide (CO). In which molecule is the CO bond shorter? In which molecule is the CO bond stronger?

Compare the nitrogen-nitrogen bond in hydrazine, \(\mathrm{H}_{2} \mathrm{NNH}_{2},\) with that in "laughing gas," \(\mathrm{N}_{2} \mathrm{O}\). In which molecule is the nitrogen-nitrogen bond shorter? In which is the bond stronger?

The compound oxygen difluoride is quite reactive, giving oxygen and HF when treated with water:$$\begin{aligned}\mathrm{OF}_{2}(\mathrm{g})+\mathrm{H}_{2} \mathrm{O}(\mathrm{g}) & \longrightarrow \mathrm{O}_{2}(\mathrm{g})+2 \mathrm{HF}(\mathrm{g}) \\\\\Delta H_{\mathrm{rxn}}^{\circ} &=-318 \mathrm{kJ}\end{aligned}$$.Using bond energies, calculate the bond dissociation energy of the \(\mathbf{O}-\) F bond in \(\mathrm{OF}_{2}\).

Specify the number of valence electrons for \(\mathrm{Li}, \mathrm{Ti}, \mathrm{Zn}, \mathrm{Si}\) and Cl.

Describe the formation of KF from K and F atoms using Lewis symbols. Is bonding in KF ionic or covalent?