Chapter 8

Give the periodic group number and number of valence electrons for each of the following atoms. (a) 0 (b) \(B\) (c) \(\mathrm{Na}\) (d) \(\mathrm{Mg}\) (e) \(\mathbf{F}\) (f) \(\mathrm{S}\)

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

For elements in Groups \(4 \mathrm{A}-7 \mathrm{A}\) 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) \(\mathbf{C}\) (b) \(\mathrm{P}\) (c) 0 (d) \(\mathrm{F}\) (e) Cl (f) \(\mathrm{B}\) (g) \(\mathrm{Se}\) (h) Sn

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) \(\overline{\mathrm{BF}}_{4}^{-}\) (c) HNO \(_{2}\) (where the arrangement of atoms is HONO) (d) OSCl \(_{2}\) (where \(S\) is the central atom)

Draw a Lewis structure for each of the following molecules: (a) chlorodifluoromethane, CHCIF \(_{2}\) (C is the central atom) (b) acetic acid, \(\mathrm{CH}_{3} \mathrm{CO}_{2} \mathrm{H}\) (basic structure pictured below) (IMAGE NOT COPY) (c) acetonitrile, \(\mathrm{CH}_{3} \mathrm{CN}\) (the framework is \(\mathrm{H}_{3} \mathrm{C}-\mathrm{C}-\mathrm{N}\) ) (d) allene, \(\mathrm{H}_{2} \mathrm{CCCH}_{2}\)

Draw a Lewis structure for each of the following molecules: (a) methanol, \(\mathrm{CH}_{3} \mathrm{OH}\) (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 (IMAGE NOT COPY)

Show all possible resonance structures for each of the following molecules or ions: (a) sulfur dioxide, \(\mathrm{SO}_{2}\) (b) nitrous acid, HNO \(_{2}\) (c) thiocyanate ion, \(\mathrm{SCN}^{-}\)

Show all possible resonance structures for each of the following molecules or ions: (a) nitrate ion, \(\mathrm{NO}_{3}^{-}\) (b) nitric acid, \(\mathrm{HNO}_{3}\) (c) nitrous oxide (laughing gas), \(\mathrm{N}_{2} \mathrm{O}\) (where the bonding is in the order \(\mathrm{N}-\mathrm{N}-\mathrm{O}\) )

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) \(\mathrm{BrF}_{2}^{+}\)

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

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

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

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) \(\mathrm{NH}_{2} \mathrm{Cl}\) (b) \(\mathrm{Cl}_{2} \mathrm{O}\) ( \(\mathrm{O}\) 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) ClF \(_{3}\) (c) \(\mathrm{ClF}_{4}^{-}\) (d) ClF \(_{5}\)

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) \(\mathrm{SiF}_{6}^{2-}\) (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 \(\mathrm{Cl}_{2} \mathrm{CO}\) (d) \(\mathrm{H}-\mathrm{C}-\mathrm{H}\) (angle 1 ) and \(\mathrm{C}-\mathrm{C} \equiv \mathrm{N}\) (angle 2 ) in acetonitrile (IMAGE NOT COPY)

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 \(\mathrm{C}-\mathrm{N}\) (b) \(\mathrm{P}-\mathrm{Br}\) and \(\mathrm{P}-\mathrm{Cl}\) (c) \(\mathrm{B}-\mathrm{O}\) and \(\mathrm{B}-\mathrm{S}\) (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) \(\mathbf{C}-\mathbf{N}\) (b) \(\mathbf{C}-\mathbf{H}\) (c) \(\mathrm{C}-\mathrm{Br}\) (d) \(\mathrm{S}-\mathrm{O}\)

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) \(\mathrm{H}_{3} \mathrm{O}^{+}\) (b) \(\mathrm{NH}_{4}^{+}\) (c) \(\mathrm{NO}_{2}^{+}\) (d) \(\mathrm{NF}_{4}^{+}\)

Three resonance structures are possible for dinitrogen monoxide, \(\mathrm{N}_{2} \mathrm{O}\) (a) Draw the three resonance structures. (b) Calculate the formal charge on each atom in each resonance structure. (c) Based on formal charges and electronegativity, 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 C atom?

The chemistry of the nitrite ion and HNO \(_{2}:\) (a) 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. (b) If an \(\mathrm{H}^{+}\) ion is attached to \(\mathrm{NO}_{2}^{-}\) (to form the acid \(\left.\mathrm{HNO}_{2}\right),\) it attaches to the \(\mathrm{O}\) atom and not the \(\mathrm{N}\) atom. Explain why you would predict this structure. (c) Two resonance structures are possible for HNO,. Draw these structures, and then find the formal charge on each atom in each resonance structure. Is either of these structures strongly preferred over the other?

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 C or O?

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

Consider the following molecules: (a) \(\mathrm{CH}_{4}\) (b) \(\mathrm{NH}_{2} \mathrm{Cl}\) (c) \(\mathrm{BF}_{3}\) (d) \(\mathrm{CS}_{2}\) (i) In which compound are the bonds most polar? (ii) Which compounds are not polar? (iii) Are the \(\mathrm{H}\) atoms in \(\mathrm{NH}_{2} \mathrm{Cl}\) negative or positive?

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) \(\mathrm{BeCl}_{2}\) (b) \(\mathrm{HBF}_{2}\) (c) \(\mathrm{CH}_{3} \mathrm{Cl}\) (d) \(\mathrm{SO}_{3}\)

Which of the following molecules is (are) not polar? For each polar molecule, indicate the direction of polarity-that is, which is the negative end and which is the positive end. (a) CO (b) \(\mathrm{BCl}_{3}\) (c) \(\mathrm{CF}_{4}\) (d) \(\mathrm{PCl}_{3}\) (e) \(\mathrm{GeH}_{4}\)

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

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

In boron compounds, the B atom often is not surrounded by four valence electron pairs. Illustrate this with BCl \(_{3} .\) Show how the molecule can achieve an octet configuration by forming a coordinate covalent bond with ammonia (NH \(_{3}\) ).

Which of the following compounds or ions do not have an octet of electrons surrounding the central atom: \(\mathrm{BF}_{4}^{-}, \mathrm{SiF}_{4}, \mathrm{SeF}_{4}, \mathrm{BrF}_{4}^{-}, \mathrm{XeF}_{4} ?\)

In which of the following does the central atom obey the octet rule: \(\mathrm{NO}_{2}, \mathrm{SF}_{4}, \mathrm{NH}_{3}, \mathrm{SO}_{3}, \mathrm{ClO}_{2},\) and \(\mathrm{ClO}_{2}^{-} ?\) Are any of these species odd- electron molecules or ions?

Draw resonance structures for the formate ion, \(\mathrm{HCO}_{2}^{-}\) and then determine the \(\mathrm{C}-\mathrm{O}\) bond order in the ion.

Consider a series of molecules in which carbon is attached by single covalent bonds to atoms of secondperiod elements: \(\mathrm{C}-\mathrm{O}, \mathrm{C}-\mathrm{F}, \mathrm{C}-\mathrm{N}, \mathrm{C}-\mathrm{C},\) and \(\mathrm{C}-\mathrm{B}\) Place these bonds in order of increasing bond length.

To estimate the enthalpy change for the reaction $$\mathrm{O}_{2}(\mathrm{g})+2 \mathrm{H}_{2}(\mathrm{g}) \rightarrow 2 \mathrm{H}_{2} \mathrm{O}(\mathrm{g})$$ what bond dissociation enthalpies do you need? Outline the calculation, being careful to show correct algebraic signs.

Draw Lewis structures (and resonance structures where appropriate) for the following molecules and ions. What similarities and differences are there in this series? (a) \(\mathrm{CO}_{2}\) (b) \(\mathrm{N}_{3}^{-}\) (c) \(\mathrm{OCN}^{-}\)