CHEM 1411 - Ch 7 Part A

Select all the options that correctly describe the bond angles associated with each electron-domain geometry.

-A bond angle of 180o is observed for a linear system. -The trigonal bipyramidal system has two different bond angles. -A species with 3 electron domains will exhibit an ideal bond angle of 120o.

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.

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

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

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

Match each number of electron domains with the correct electron-domain geometry. 1. linear 2. trigonal planar 3. tetrahedral 4. trigonal bipyramidal 5. octahedral

1. 2 domains 2. 3 domains 3. 4 domains 4. 5 domains 5. 6 domains

Match each molecular geometry correctly to the electron-domain arrangement described. 1. linear 2. seesaw 3. square planar 4. bent 5. trigonal pyramidal

1. 5 electron domains; 3 lone pairs 2. 5 electron domains; 1 lone pair 3. 6 electron domains; 2 lone pairs 4. 4 electron domains; 2 lone pairs 5. 4 electron domains; 1 lone pair

Match each ideal bond angle with the correct electron-domain geometry in each case. 1. 90 2. 120 3. 109.5 4. 180 6. 90 and 120

1. octahedral 2. trigonal planar 3. tetrahedral 4. linear 5. trigonal bipyramidal

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

Which statement correctly explains how polarizability affects intermolecular forces?

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

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

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

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.

dipole; ionic

The electron-domain geometry of a species is the arrangement of electron ___ around the central atom, whereas the molecular geometry is the arrangement of bonded ___. Two species with the same electron-domain geometry may have different molecular geometries.

domains; atoms

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.

electrons; polarized; stronger

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

Molecular shape is determined by the number of electron domains around a central atom, where an electron domain may be a(n) ___ electron pair of any ___ between two atoms.

lone; bond

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.

nitrogen; electrons; hydrogen

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 ___.

nonpolar; gases

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.

temporary; dispersion

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

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

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.

bonded; lone

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.

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

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

Molecular geometry is specified for a central atom in a structure. A "central" atom is _____.

any atom that is bonded to two or more other atoms

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

b c d

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.

covalent; intermolecular

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

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

Why is BeF2 a nonpolar molecule?

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

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

False

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.

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

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

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

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

Select all the correct statements regarding ion-dipole interactions.

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

Match each molecular geometry correctly to the electron-domain arrangement described. 1. bent 2. T-shaped 3. square pyramidal 4. tetrahedral 5. linear

1. 3 electron domains; 1 lone pair 2. 5 electron domains; 2 lone pairs 3. 6 electron domains; 1 lone pair 4. 4 electron domains; 0 lone pairs 5. 2 electron domains; 0 lone pairs

Molecular shapes can be classified using the general designation ABx. Match each symbol in this designation with its correct meaning. 1. A 2. B 3. x

1. central atom in structure 2. terminal atom 3. number of terminal atoms

Match each description of molecular shape to the correct implication for polarity. 1. Individual bond dipoles will cancel 2. Individual bond dipoles will not cancel 3. A species will be nonpolar overall 4. A species will be polar overall

1. for a species that has identical bonds and a symmetrical geometry 2. for a species with an unsymmetrical geometry 3. if individual bond dipoles cancel 4. if individual bond dipoles do not cancel

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

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.

negative; dipole-dipole