CHEMISTRY 111 Chapter 7

Organize the steps for determining molecular shape in the correct order, starting with the first step at the top of the list.

1. Use the molecular formula to draw a Lewis structure. 2. Count the number of electron domains on the central atom. 3. Determine the electron-domain geometry 4. Determine the molecular shape

The Lewis structure for one of the resonance forms of the sulfate ion, SO42-, is shown. What is the approximate value of the marked O-S-O bond angle?

109.5

The Lewis structure for the AsF5 is shown. The approximate value of the bond angle marked "a" is equal to _____ while the approximate value of the bond angle marked "b" is equal to _____. (Remember that this species has a three-dimensional shape, as indicated by the wedged and dashed bonds.)

90o, 120o

Select all that apply Which of the following compounds exhibit hydrogen bonding between their molecules? Select all that apply.

A B E

Which of the following compounds exhibit hydrogen bonding between their molecules? Select all that apply.

A B E

Which statement correctly explains how polarizability affects intermolecular forces?

A more polarizable molecule experiences stronger dispersion forces and therefore stronger intermolecular forces overall.

Select all that apply Select all the correct statements regarding ion-dipole interactions.

An ion-dipole interaction exists between an ion and a polar molecule. Ion-dipole interactions only occur in mixtures. Ion-dipole interactions are responsible for the solubility of ionic compounds in aqueous solutions. The magnitude of ion-dipole interactions is inversely proportional to the size of the polar molecule.

Select all the statements that correctly describe the five basic electron-domain geometries.

An octahedral geometry indicates that there are six electron domains. A system with three electron domains will have a trigonal planar electron-domain arrangement.

Why is BeF2 a nonpolar molecule?

BeF2 is linear and therefore the individual bond dipoles cancel to give no net dipole.

Most covalently bonded substances consist of individual separate molecules. Each individual molecule is held together by means of strong bonds between the atoms. In addition, there are weak forces of attraction between the individual molecules, called forces.

Blank 1: covalent Blank 2: intermolecular

The attraction between an ion and a nearby polar molecule is called an ion - interaction. This attractive force is important when a(n) compound dissolves in a polar solvent such as H2O.

Blank 1: dipole Blank 2: ionic

The strength of dispersion forces between two species depends on the mobility of their . The larger an atom or molecule, the more easily it becomes , and the the dispersion forces it exhibits.

Blank 1: electrons Blank 2: polarized Blank 3: stronger, greater, larger, or higher

A momentary change in the electron density surrounding an atom or a molecule causes it to have a(n) dipole even if it is not normally polar. This induces a similar effect in a nearby molecule or atom and there will be a weak attraction between the two particles as a result. These weak interactions are called forces or London forces.

Blank 1: instantaneous, temporary, induced, momentary, or transient Blank 2: dispersion or London dispersion

When two polar molecules are close together, the partial positive charge on one molecule will attract the partial charge on the other. This type of intermolecular force is called a - attraction.

Blank 1: negative or - Blank 2: dipole Blank 3: dipole

When a hydrogen atom is covalently bonded to either oxygen, , or fluorine there will be an attraction between that hydrogen and a lone pair of on a nitrogen, oxygen, or fluorine atom on an adjacent molecule. This attraction is called a bond.

Blank 1: nitrogen or N Blank 2: electrons or e- Blank 3: hydrogen or H

Dispersion forces are the only type of intermolecular force exhibited by atoms and by molecules. Without the existence of dispersion forces, such substances would only exist as .

Blank 1: nonpolar or non-polar Blank 2: gases

Consider the molecule CCl4. Each C-Cl bond in this molecule is because the electronegativity difference between C and Cl is equal to 0.5. Since CCl4 is tetrahedral in shape and symmetrical, the individual bond dipoles and the molecule is overall.

Blank 1: polar or polar covalent Blank 2: cancel, cancel out, or sum to zero Blank 3: nonpolar or non-polar

Select all that apply Which of the following statements correctly describe dispersion or London forces? Select all that apply.

Dispersion forces are a weak attraction between temporary dipoles. All covalent compounds exhibit dispersion forces.

Select all that apply Select all the statements that correctly describe the bonding in the molecule PF3 in terms of valence bond theory.

Each P-F bond is formed by the overlap of a 3p orbital from P with a 2p orbital from F. VB theory predicts that the bond angles in PF3 will be close to 90.

Which statement correctly describes the basic principle of VSEPR theory?

Each group of valence electrons around a central atom is located as far from the others as possible.

True or false: A bond between O and H within any molecule is called a hydrogen bond.

False

True or false: Any molecule in which all of the bonds are identical will be nonpolar

False

Select all that apply Which of the following statements correctly describe how to determine whether a given molecule is polar or nonpolar? Select all that apply.

If the individual bond dipoles cancel, the molecule is nonpolar. If a molecule contains no dipole moments across any bonds it will be nonpolar. For a molecule that has polar bonds, the molecular geometry must be known in order to predict the overall polarity.

Select all that apply Select all the statements that correctly describe the arrangement of lone pairs in systems with 5 and 6 electron domains

In a trigonal bipyramidal system lone pairs prefer to occupy equatorial positions. If there are two lone pairs in an octahedral system they will be located opposite each other.

Match each description of molecular shape to the correct implication for polarity.

Individual bond dipoles will cancel for a species that has identical bonds and a symmetrical geometry. Individual bond dipoles will not cancel for a species with an unsymmetrical geometry. A species will be nonpolar overall if individual bond dipoles cancel. A species will be polar overall if individual bond dipoles do not cancel.

Which of the following statements correctly defines intermolecular forces?

Intermolecular forces are the weak forces of attraction found between the individual molecules of a molecular covalent substance.

Select all that apply Which of the following options correctly reflect the relationship between dispersion forces and particle size? Select all that apply.

Larger particles are more polarizable and experience stronger dispersion forces. For molecules of similar shape, dispersion forces tend to increase with increasing molar mass.

Select all the statements that correctly explain why bond angles in molecules containing lone pairs or multiple bonds may be different than the VSEPR ideal.

Multiple bonds contain higher electron densities that repel more than single bonds. Multiple bonds repel more strongly than single bonds that results in compression in adjacent bond angles. Lone pairs exert greater repulsion that causes compression in adjacent bond angles.

Select all that apply Which species has a net dipole moment (i.e., are polar overall)? Select all that apply.

NBr3 CH2Cl2

Select all that apply Which of the following options correctly describe the NH2-CH=O structure? Select all that apply.

Nitrogen will have a trigonal pyramidal molecular geometry. Carbon will have a trigonal planar molecular geometry.

Which of the following correctly describes the bond angle in a molecule of the general type ABx?

The angle between two adjacent A-B bonds

Select all that apply Which of the following options correctly describe the structure shown? Select all that apply.

The bond angles around C2 are approximately equal to 180°. C1 will have a tetrahedral geometry. C2 will have a linear geometry.

Select all that apply Which of the following aspects of bonding are addressed by valence bond theory, but are NOT addressed by Lewis bond theory?

The differences in length between various single bonds The energetics of bond formation

Select all that apply Select all the statements that correctly describe how to determine the molecular shape of a species using VSEPR.

The total number of shared and unshared electron pairs around the central atom gives the electron-domain geometry. Use the molecular formula to draw the Lewis structure. If unshared electron pairs are present, the molecular geometry will differ from the electron-domain geometry.

Select all that apply Select all the statements that correctly describe dipole-dipole attractions.

These are the forces of attraction between two polar molecules. For two compounds of similar molar mass, the greater the molecular dipole moment, the stronger the dipole-dipole attraction.

Select all the statements that correctly describe dipole-dipole attractions.

These are the forces of attraction between two polar molecules. For two compounds of similar molar mass, the greater the molecular dipole moment, the stronger the dipole-dipole attraction.

True or false: Dispersion forces are exhibited by both polar and nonpolar molecules.

True

True or false: When using VSEPR theory to determine molecular shape, a triple bond counts as a single electron domain even though it consists of 3 shared electron pairs.

True

Select all that apply Select all the statements that correctly describe how to determine the molecular shape of a species using VSEPR.

Use the molecular formula to draw the Lewis structure. If unshared electron pairs are present, the molecular geometry will differ from the electron-domain geometry. The total number of shared and unshared electron pairs around the central atom gives the electron-domain geometry.

Select all that apply Which of the following statements are correct with regard to Lewis bonding theory and valence bonding theory?

Valence bond theory can make predictions about bond angles that Lewis theory cannot. Lewis theory does not explain differences in bond strength, while valence bond theory does.

Select all that apply Select all the statements that correctly describe the bonding in the molecule HCl in terms of valence bond theory.

Valence bond theory predicts the potential energy is a minimum for an optimal orbital overlap for H and Cl. The H-Cl bond is formed by the overlap of a 3p orbital from Cl with a 1s orbital from H.

Which of the following marked bonds are hydrogen bonds? Select all that apply.

b d

Select all that apply Select all the lettered options that correspond to equatorial positions in the image shown.

b,c,d

Match each molecular geometry correctly to the electron-domain arrangement described.

bent 3 electron domains; 1 lone pair T-shaped 5 electron domains; 2 lone pairs square pyramidal 6 electron domains; 1 lone pair tetrahedral 4 electron domains; 0 lone pairs linear 2 electron domains; 0 lone pairs

In an ABx molecule, the angle between two adjacent A-B bonds is called the ____ angle. This angle is determined by the number of _____ domains or groups surrounding the central atom.

bond, electron

The molecular shape of a species, which is the arrangement of the bonded atoms around the central atom, is determined not only by the number of ______ electron domains that join the atoms, but by the number of _______ electron domains as well, since these electrons also occupy space.

bonding, nonbonding

A 5-electron domain system (shown) has two different types of positions for electron domains. The three positions marked "1" form a trigonal plane about the central atom and are called ______ positions, while the two positions marked "2" are ______ positions.

equatorial, axial

The larger a molecule or atom, the _____ the number of electrons and the _____ polarizable it will generally be. The strength of the dispersion forces for a particular substance therefore generally _____ as molar mass increases, providing molecules of similar shape are compared.

greater; more; increases

Match each number of electron domains with the correct electron-domain geometry.

linear 2 domains trigonal planar 3 domains tetrahedral 4 domains trigonal bipyramidal 5 domains octahedral 6 domains

Match each molecular geometry correctly to the electron-domain arrangement described.

linear 5 electron domains; 3 lone pairs seesaw 5 electron domains; 1 lone pair square planar 6 electron domains; 2 lone pairs bent 4 electron domains; 2 lone pairs trigonal pyramidal 4 electron domains; 1 lone pair

In general, a lone pair repels bonding electron pairs _____ than bonding pairs repel each other. A lone pair will therefore _____ the bond angle between bonding pairs. A double bond has a similar effect.

more, decrease