Chapter 9

Sketch the following molecular shapes and give the various bond angles in the structures: (a) planar triangular, (b) tetrahedral, (c) octahedral.

Sketch the following molecular shapes and give the bond angles in the structures: (a) linear, (b) trigonal bipyramidal.

What is the underlying principle on which the VSEPR model is based?

What is an electron domain? How are nonbonding and double bonds described by electron domains?

How many bonding domains and how many nonbonding domains are there in a molecule of formaldehyde, HCHO?

Sketch the following molecular shapes and give the various bond angles in the structure: (a) T-shaped, (b) seesaw shaped, and (c) square pyramidal.

What arrangements of domains around an atom are expected when there are (a) three domains, (b) six domains, (c) four domains, or (d) five domains?

How do we indicate a bond dipole when we draw the structure of a molecule?

Under what conditions will a molecule be polar?

What condition must be met if a molecule having polar bonds is to be non polar?

What is meant by orbital overlap?

Sketch figures that illustrate the directional properties of the following hybrid orbitals: (a) \(s p\), (b) \(s p^{2}\), (c) \(s p^{3}\).

Why do Period 2 elements never use \(s p^{3} d\) or \(s p^{3} d^{2}\) hybrid orbitals for bond formation?

What relationship is there, if any, between Lewis structures and the valence bond descriptions of molecules?

How can the VSEPR model be used to predict the hybridization of an atom in a molecule?

Using orbital diagrams, describe how sp \(^{3}\) hybridization occurs in each atom: (a) carbon, (b) nitrogen, (c) oxygen. If these elements use \(s p^{3}\) hybrid orbitals to form bonds, how many lone pairs of electrons would be found on each?

Sketch the way the orbitals overlap to form the bonds in each of the following: (a) \(\mathrm{CH}_{4},\) (b) \(\mathrm{NH}_{3}\), (c) \(\mathrm{H}_{2} \mathrm{O}\). (Assume the central atom uses hybrid orbitals.)

What two basic shapes have hybridizations that include \(\bar{d}\) orbitals??

The ammonia molecule, \(\mathrm{NH}_{3}\), can combine with a hydrogen ion, \(\mathrm{H}^{+}\) (which has an empty 1 s orbital), to form the ammonium ion, \(\mathrm{NH}_{4}^{+}\). (This is how ammonia can neutralize acid and therefore function as a base.) Sketch the geometry of the ammonium ion, indicating the bond angles.

Why can free rotation occur easily around a \(\sigma\) -bond axis but not around a \(\pi\) -bond axis?

Explain why \(\mathrm{He}_{2}\) does not exist but \(\mathrm{H}_{2}\) does.

How does MO theory account for the paramagnetism of \(\mathrm{O}_{2} ?\)

What relationship is there between bond order and bond energy?

What is the theoretical basis of both valence bond \((\mathrm{VB})\) theory and molecular orbital (MO) theory?

What shortcomings of Lewis structures and VSEPR theory do \(\mathrm{VB}\) and \(\mathrm{MO}\) theories attempt to overcome?

What is the main difference in the way VB and MO theories view the bonds in a molecule?

What effect does delocalization have on the stability of the electronic structure of a molecule?

What is a conduction band? What is a valence band?

On the basis of the band theory of solids, how do conductors, insulators, and semiconductors differ?

Why does electrical conductivity in semiconductors increase with increasing temperature?

What are allotropes? How do they differ from isotopes?

Describe the structure of diamond. What kind of hybrid orbitals does carbon use to form bonds in diamond? What is the geometry around carbon in this structure?

Describe the structure of graphene. What kind of hybrid orbitals does carbon use in the formation of the molecular framework of graphene?

How is the structure of graphite related to the structure of graphene?

How is the structure of a carbon nanotube related to the structure of graphene?

What are the different allotropes of phosphorus?

What are the two allotropes of oxygen?

What beneficial function does ozone serve in earth's upper atmosphere?

Predict the shapes of (a) \(\mathrm{NH}_{2}^{-}\), (b) \(\mathrm{CO}_{3}^{2-}\), (c) \(\mathrm{IF}_{3},\) (d) \(\mathrm{Br}_{3}^{-},\) and (e) \(\mathrm{GaH}_{3}\).

Predict the shapes of (a) \(\mathrm{SF}_{3}^{+}\), (b) \(\mathrm{GeF}_{4}\) (c) \(\mathrm{SO}_{4}^{2-}\), (d) \(\mathrm{O}_{3},\) and (e) \(\mathrm{N}_{2} \mathrm{O}\).

Predict the shapes of (a) \(\mathrm{FCl}_{2}^{+},\) (b) \(\mathrm{AsF}_{5},\) (c) \(\mathrm{AsF}_{3}\), (d) \(\mathrm{SbH}_{3}\), and (e) \(\mathrm{SeO}_{2}\).

Predict the shapes of (a) \(\mathrm{TeF}_{4}\), (b) \(\mathrm{SbCl}_{6}\) (c) \(\mathrm{NO}_{2},\) (d) \(\mathrm{PCl}_{4}\), and (e) \(\mathrm{PO}_{4}^{3-}\).

Predict the shapes of (a) \(\mathrm{IO}_{4}^{-},(\mathbf{b}) \mathrm{IF}_{4}^{-},(\mathbf{c}) \mathrm{TeF}_{6},(\mathbf{d}) \mathrm{SiO}_{4}\) and (e) \(\mathrm{ICl}_{2}\).

Predict the shapes of (a) \(\mathrm{CS}_{2},\) (b) \(\mathrm{BrF}_{4}^{-},\) (c) \(\mathrm{ICl}_{3}\), (d) \(\mathrm{ClO}_{3}^{-},\) and (e) \(\mathrm{SeO}_{3}\).

Ethene, also called ethylene, is a gas used to ripen tomatoes artificially. It has the Lewis structure: What would you expect the \(\mathrm{H}-\mathrm{C}-\mathrm{H}\) and \(\mathrm{H}-\mathrm{C}=\mathrm{C}\) bond angles to be in this molecule? (Caution: Don't be fooled by the way the structure is drawn here.)

Ethyne, more commonly called acetylene, is a gas used in welding torches. It has the Lewis structure \(\mathrm{H}-\mathrm{C} \equiv \mathrm{C}-\mathrm{H}\). What would you expect the \(\mathrm{H}-\mathrm{C}-\mathrm{C}\) bond angle to be in this molecule?

Which of the following molecules would be expected to be polar? (a) \(\mathrm{PBr}_{3},\) (b) \(\mathrm{SO}_{3},\) (c) \(\mathrm{AsCl}_{3},\) (d) \(\mathrm{ClF}_{3},\) (e) \(\mathrm{BCl}_{3}\).

Which of the following molecules or ions would be expected to have a net dipole moment? (a) \(\mathrm{H}_{2} \mathrm{~S},(\mathbf{b}) \mathrm{BeH}_{2},\) (c) \(\mathrm{SCN}^{-}\), (d) \(\mathrm{CN}^{-}\), (e) \(\mathrm{BrCl}_{3}\)

Explain why \(\mathrm{SF}_{6}\) is nonpolar, but \(\mathrm{SF}_{5} \mathrm{Br}\) is polar.

Explain why \(\mathrm{CH}_{3} \mathrm{Cl}\) is polar, but \(\mathrm{CCl}_{4}\) is not.