Chapter 20

Discuss the factors that cause the chemistry of the elements in the second period to be different from that of the elements in the same group in later periods.

Why do elements of the second period form stronger \(\pi\) bonds than elements of the third period? Give a specific example of a structural contrast between elemental forms from a single group that can be explained by this difference.

Compare the electronegativities and ionization energies of metals and nonmetals.

Why does sulfur form expanded valence shell compounds such as \(\mathrm{SF}_{6}\), whereas oxygen does not?

Three different bonding modes occur for hydrogen. Describe them and give a specific example of each.

Describe the bonding of the hydrogen in (a) \(\mathrm{KH}\) (b) \(\mathrm{HCl}\) (c) \(\mathrm{H}_{2}\)

Why does \(\mathrm{H}_{2}\) have such a low boiling point \(\left(-253{ }^{\circ} \mathrm{C}\right)\) ?

List the symbols of the three isotopes of hydrogen and the approximate abundance of each.

Why is helium rather than hydrogen currently used as the gas in blimps?

What is the main difference between saturated and unsaturated cooking oils?

What is the inert pair effect? How does it affect the chemistry of Group \(3 \mathrm{~A}\) ?

Classify the Group 3 A elements as nonmetals, metals, or metalloids.

What unusual structural feature is found in the elemental forms of boron?

Explain why aluminum, a reactive metal, can be used in airplanes and on the exteriors of houses, where it is exposed to the oxygen in the air.

Explain why Group \(4 \mathrm{~A}\) elements, especially carbon and silicon, are ideally suited to making four electron-pair bonds.

State three commercial uses for graphite.

What is meant by the term adsorption, and why does activated charcoal have high adsorption qualities?

How does doping silicon with phosphorus change its conducting properties?

A Describe the Haber process for the synthesis of ammonia. Be sure to comment on the positive and negative effects that Le Chatelier's principle has on the production of ammonia by this process.

Even though phosphates are found widely in most soils, fertilizers are used to supply additional phosphates. What is the problem with the "natural phosphates," and how is this problem overcome in commercial fertilizers?

Briefly outline the important physical and chemical properties of the two main allotropes of oxygen.

Why are elements in Group 8 A expected to be monomeric and relatively nonreactive?

What is the main source of radon in homes?

Of the following pairs of elements, which element is more likely to be able to form a double bond with carbon? (a) nitrogen or phosphorus (b) oxygen or sulfur

Of the following pairs of elements, which element is more likely to be able to form a double bond with oxygen? (a) carbon or silicon (b) oxygen or sulfur

From the elements nitrogen, silicon, and gallium, pick the ones with the most and the least metallic properties. Explain your choices.

From the elements silicon, germanium, and tin, pick the ones with the most and the least metallic properties. Explain your choices.

Write the equation for the reaction of \(\mathrm{NaH}\) and water. What mass of \(\mathrm{NaH}\) is needed to prepare \(1.00 \mathrm{~L}\) hydrogen gas at \(25^{\circ} \mathrm{C}\) and 1.00 atm pressure?

Write the equation for the reaction of zinc metal with hydrochloric acid. What mass of zinc metal is needed to prepare \(1.00 \mathrm{~L}\) hydrogen gas at \(25^{\circ} \mathrm{C}\) and \(1.00 \mathrm{~atm}\) pressure, assuming excess \(\mathrm{HCl}\) ?

Give two important industrial preparations for \(\mathrm{H}_{2}\).

What is the most important industrial use of \(\mathrm{H}_{2}\) ? Write the equation for this use.

Write the equation for the water-gas shift reaction.

Write a series of equations that shows how coal plus water can be converted to methanol. Be careful to balance all equations.

Draw the structure of \(\mathrm{B}_{2} \mathrm{H}_{6}\), and describe the bonding in this molecule. What is the hybridization at the boron atoms?

Describe the bonding in \(\mathrm{BCl}_{3}\). What is the hybridization at the boron atom? Is the boron really electron deficient?

What is a three-center, two-electron bond?

How does a three-center, two-electron bond differ from a normal two-center, two-electron bond?

Because of the high reactivity of the boron hydrides with oxygen, they were considered as possible solid rocket fuels. Write the equation for the reaction of oxygen with \(\mathrm{B}_{10} \mathrm{H}_{14}\) (a solid at room temperature).

Write the equation and describe the changes in hybridization of the boron atom in the reaction between \(\mathrm{BCl}_{3}\) and \(\mathrm{NH}_{3}\)

Describe the Hall process for the production of aluminum from the mineral bauxite. How is energy saved by recycling aluminum rather than preparing it by the Hall process?

Describe the composition of a ruby.

Draw the structure of \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\). Compare the bonding in \(\mathrm{Al}_{2} \mathrm{Cl}_{6}\) and \(\mathrm{B}_{2} \mathrm{H}_{6}\).

The oxide \(\mathrm{Ga}_{2} \mathrm{O}_{3}\) is amphoteric. Write an equation for its reactions, if any, with \(\mathrm{HCl}\) and \(\mathrm{NaOH}\).

What are hybridizations of silicon and carbon in \(\mathrm{SiO}_{2}\) and \(\mathrm{CO}_{2}\) ?

Draw the structure of silica, \(\mathrm{SiO}_{2}\), and compare it with the structure of \(\mathrm{CO}_{2}\). Why are the structures so different?

Describe a \(p\) -type semiconductor based on silicon.

Describe an \(n\) -type semiconductor based on silicon.

What is the hybridization of silicon in \(\mathrm{SiCl}_{4}\) ? Is this compound polar or nonpolar?

\text { What is the hybridization of silicon in silicates? }

What are the structures of the most common allotropic forms of nitrogen and phosphorus? Explain why they are so different.