Chapter 5

Give the proper name for each compound and indicate whether it is ionic or polar covalent: (a) \(\mathrm{NH}_{4} \mathrm{I}\) (b) \(\mathrm{Cl}_{2} \mathrm{O}_{7}\) (c) \(\mathrm{SrCl}_{2}\) (d) \(\mathrm{Li}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\)

Give the formula for each compound and indicate whether it is ionic or polar covalent: (a) Copper(I) sulfide (electronegativity of Cu is 1.9) (b) Aluminum carbide (c) Diiodine pentoxide (d) Chlorine trifluoride

Arrange the following sets of bonds in order of increasing ionic character. Use the symbols \(\delta+\) and \(\delta-\) to indicate partial charges, if any, in the bonds: \(\mathrm{O}-\mathrm{Cl}, \mathrm{C}-\mathrm{F}, \mathrm{N}-\mathrm{Cl}, \mathrm{O}-\mathrm{H}, \mathrm{S}-\mathrm{O}\)

Hydrogen sulfide and hydrosulfuric acid have the same molecular formula. How are they different?

Using only the periodic table, determine which bond in each pair is more ionic: (a) \(\mathrm{H}-\mathrm{F}\) or \(\mathrm{H}-\mathrm{Cl}\) (b) \(\mathrm{O}-\mathrm{F}\) or \(\mathrm{C}-\mathrm{F}\)

The polyatomic ion \(\mathrm{MnO}_{4}^{2-}\) is listed in your book as permanganate. What would be the name of \(\mathrm{MnO}_{3}^{2-} ?\)

It is convenient to classify substances as ionic or covalent. How would you classify sodium sulfate? Explain fully.

\(\mathrm{P}\) is immediately under \(\mathrm{N}\) in the periodic table. Both react with three atoms of chlorine to form \(\mathrm{NCl}_{3}\) and \(\mathrm{PCl}_{3} .\) However, phosphorus also forms \(\mathrm{PCl}_{5}\), whereas nitrogen does not. Draw dot diagrams for all three molecules. In doing so, you will have to violate the octet rule for \(\mathrm{PCl}_{5}\). That is OK. Do it. Then explain why phosphorus can do this but nitrogen can't. (Hint: Nitrogen has only \(2 \mathrm{~s}\) and \(2 p\) orbitals in its valence shell, which together can hold a maximum of eight electrons. Read section \(5.8\) about expanded octet atoms.) Then postulate what kind of atoms might be expected to exceed the octet rule.

Give an example of a covalent compound that, upon dissolving in water, yields ions. Write a reaction to show this transformation and classify the starting compound.

Draw a diagram that shows both the covalent and ionic nature of the compound sodium azide, formula \(\mathrm{NaN}_{3}\) (the \(\mathrm{N}_{3}\) portion is linear in shape). If there are resonance forms, then include them.

Benzene, formula \(\mathrm{C}_{6} \mathrm{H}_{6}\), is a perfect closed hexagon of carbon atoms, each with one hydrogen atom attached. Draw a dot diagram for this molecule, and include any resonanace forms if

Draw a dot diagram for selenium hexafluoride and explain how it violates the octet rule.

Consider the \(\mathrm{PO}_{4}^{3}\) phosphate anion. (a) Draw a dot diagram that obeys the octet rule for all of the atoms. (b) Suppose the actual bond order for the \(\mathrm{P}-\mathrm{O}\) bonds was \(1.25 .\) Draw a dot diagram that explains this, using the concept of expanded octet and resonance. Also state whether expanding the octet as you have shown would be allowed, and why.

Consider sulfur trioxide. (a) Draw a dot diagram that obeys the octet rule for all of the atoms. (b) Suppose the actual bond order for the \(\mathrm{S}-\mathrm{O}\) bonds was \(2 .\) Draw a dot diagram that explains this, using the concept of expanded octet. Also state whether expanding the octet as you have shown would be allowed, and why.

Does \(\mathrm{BeH}_{2}\) have all of its atoms obeying the octet rule? If not, indicate which atom or atoms violate the octet rule and why it is OK.

Consider two molecules, \(\mathrm{BH}_{3}\) and \(\mathrm{NH}_{3} .\) Draw dot diagrams for both and indicate which one possesses and electron deficient atom.

Draw a dot diagram for \(\mathrm{PF}_{5} .\) Which atom is an expanded octet atom?

Draw a dot diagram for \(\mathrm{BrF}_{5}\). (Hint: \(\mathrm{Br}\) is an expanded octet atom in this molecule. Don't be afraid to stick lone pairs of electrons on it if you have to.)

Draw a dot diagram for \(\mathrm{XeF}_{4}\). (Hint: Xe is an expanded octet atom in this molecule. Don't be afraid to stick lone pairs of electrons on it if you have to.)

Draw a dot diagram for \(\mathrm{I}_{3^{\prime}}\). (Hint: Then central I atom is an expanded octet atom in this molecule. Don't be afraid to stick lone pairs of electrons on it if you have to.)