Which one of these statements about formal charge is true? (a) Formal charge is the same as oxidation number. (b) To draw the best Lewis structure, you should minimize formal charge. (c) Formal charge takes into account the different electronegativities of the atoms in a molecule. (d) Formal charge is most useful for ionic compounds. (e) Formal charge is used in calculating the dipole moment of a diatomic molecule.

For each of the following ions of nitrogen and oxygen, write a single Lewis structure that obeys the octet rule, and calculate the oxidation numbers and formal charges on all the atoms: c. NO2+.

Predict the ordering, from shortest to longest, of the bond lengths in CO, CO₂, and CO₃^2- .

Consider a Lewis structure for SO3 that satisfies the octet rule. Which of the following statements is or are true?

i. SO3 has three equivalent resonance structures.

ii. There are one shorter and two longer S—O bond lengths in SO3.

iii. The S atom in SO3 has a nonzero formal charge.

Which of the following statements about benzene, C6H6, is or are true?

i. Benzene has two equivalent resonance structures.

ii. There are no nonbonding pairs in the Lewis structure for benzene.

iii. Benzene has three short and three long C—C bonds.

b. Which of these compounds or ions is an exception to the octet rule: nitrogen dioxide, borohydride (BH4−), borazine (B3N3H6 which is analogous to benzene with alternating B and N in the ring), or boron trichloride?

Draw the Lewis structures for each of the following molecules or ions. Identify instances where the octet rule is not obeyed; state which atom in each compound does not follow the octet rule; and state how many electrons surround these atoms: a. NO, b. BF₃, c. ICl₂⁻, d. OPBr₃ (the P is the central atom), e. XeF₄.

In the vapor phase, BeCl₂ exists as a discrete molecule. (a) Draw the Lewis structure of this molecule, using only single bonds. Does this Lewis structure satisfy the octet rule?

(a) Describe the molecule xenon trioxide, XeO3, using four possible Lewis structures, one each with zero, one, two, or three Xe¬O double bonds. (b) Do any of these resonance structures satisfy the octet rule for every atom in the molecule? (c) Do any of the four Lewis structures have multiple resonance structures? If so, how many resonance structures do you find? (d) Which of the Lewis structures in part (a) yields the most favorable formal charges for the molecule?

There are many Lewis structures you could draw for sulfuric acid, H₂SO₄ (each H is bonded to an O). (a) What Lewis structure(s) would you draw to satisfy the octet rule?

There are many Lewis structures you could draw for sulfuric acid, H2SO4 (each H is bonded to an O). (b) What Lewis structure(s) would you draw to minimize formal charge?

Some chemists believe that satisfaction of the octet rule should be the top criterion for choosing the dominant Lewis structure of a molecule or ion. Other chemists believe that achieving the best formal charges should be the top criterion. Consider the dihydrogen phosphate ion, H₂PO₄^-, in which the H atoms are bonded to O atoms. (b) What is the predicted dominant Lewis structure if achieving the best formal charges is the top criterion?

State whether each of these statements is true or false. e. Energy is stored in chemical bonds.

Consider the lattice energies of the following Group 2A compounds: BeH₂, 3205 kJ/mol; MgH₂, 2791 kJ/mol; CaH₂, 2410 kJ/mol; SrH₂, 2250 kJ/mol; BaH₂, 2121 kJ/mol. (a) What is the oxidation number of H in these compounds?

The ionic compound CaO crystallizes with the same structure as sodium chloride (Figure 8.3). (a) In this structure, how many O2- are in contact with each Ca2+ ion (Hint: Remember the pattern of ions shown in Figure 8.3 repeats over and over again in all three directions.)

Construct a Born–Haber cycle for the formation of the hypothetical compound NaCl₂, where the sodium ion has a 2⁺ charge (the second ionization energy for sodium is given in Table 7.2). (a) How large would the lattice energy need to be for the formation of NaCl₂ to be exothermic?

Consider the collection of nonmetallic elements O, P, Te, I, and B. (a) Which two would form the most polar single bond?

The substance chlorine monoxide, ClO(g), is important in atmospheric processes that lead to depletion of the ozone layer. The ClO molecule has an experimental dipole moment of 1.24 D, and the Cl — O bond length is 160 pm. (b) Based on the electronegativities of the elements, which atom would you expect to have a partial negative charge in the ClO molecule?

(b) Using these partial charges and the atomic radii given in Figure 7.8, estimate the dipole moment of the molecule.

(c) The measured dipole moment of BrCl is 0.57 D. If you assume the bond length in BrCl is the sum of the atomic radii, what are the partial charges on the atoms in BrCl using the experimental dipole moment?

A major challenge in implementing the 'hydrogen economy' is finding a safe, lightweight, and compact way of storing hydrogen for use as a fuel. The hydrides of light metals are attractive for hydrogen storage because they can store a high weight percentage of hydrogen in a small volume. For example, NaAlH₄ can release 5.6% of its mass as H2 upon decomposing to NaH(s), Al(s), and H₂(g). NaAlH₄ possesses both covalent bonds, which hold polyatomic anions together, and ionic bonds. (c) Based on electronegativity differences, predict the identity of the polyatomic anion. Draw a Lewis structure for this ion.

Structures A, B, and C show the connectivity of the atoms in three different molecules that are isomers of C3H4O. By completing the Lewis structures of these molecules, complete the information in the following table:

Isomer A Isomer B Isomer C

Number of single bonds

Number of double bonds

Number of triple bonds

Number of nonbonding pairs