CHEM111 6.6-7.6

Certain molecules are electron deficient, having fewer than ___ electrons around the central atom. Elements that commonly form electron deficient compounds are beryllium and ___.

8, boron

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

A bond angle of 180 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 120.

Select all the statements that correctly describe the C=N double bond in the structure shown.

The N lone pair is located in an sp2 orbital. The σ bond is formed by direct head-to-head overlap of two sp2 hybrid orbitals, one from each atom. The π bond is formed by sideways overlap of a p orbital from each atom.

Which of the following would cause the central atom in a Lewis structure to have less than a full octet of electrons? Select all that apply.

The total number of valence electrons is odd. The species has a shortage of valence electrons.

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 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

Hydrogen bonding requires H to be covalently bonded to N, O, or F. Because these elements are very ___ and ___ they effectively pull electron density from the bonded H, leaving a H nucleus (a proton). This large positive charge on tiny H allows a close and very strong attraction (H-bond) to N, O, or F on a neighboring molecule.

electronegative, small

Because lone pairs exert greater repulsions than bonded pairs, lone-pair domains always occupy the _____ positions in a trigonal bipyramid.

equatorial

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

Elements that do not obey the octet rule because they have more than eight valence electrons are said to have an ___ valence shell. This is only possible for elements that have available ___ orbitals, which are the elements found from period ___ of the periodic table onward.

expanded, d, 3

What approximate value will be observed for the bond angle marked in the structure shown? (Note that Lewis structures commonly do not reflect the actual shape of the species.)

less than 109.5

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

linear- 5 electron domains and 3 lone pairs seesaw- 5,1 square planar- 6,2 bent- 4,2 trigonal pyramidal- 4,1

A bond formed by sideways overlap of two p orbitals (one from each bonding atom) is called a(n)

pi bond

An atom or molecule that contains an odd number of valence electrons is known as a free ___

radical

The triple bond in the structure shown consists of a σ bond formed by the overlap of a(n) _____ orbital on the C with a(n) _____ orbital on the N to form the σ bond. The π bonds are formed by the overlap of two pairs of _____ orbitals.

sp, sp, p

Place the following compounds in order of increasing strength of their intermolecular forces, with the weakest at the top of the list. These compounds have approximately equal molecular masses.

1. CH3CH2CH2CH3 2. CH3CH2OCH3 3. CH3CH2CH2OH 4. CH3COOH

The Lewis structure for the molecule BBr3 is given. The B atom in this structure is surrounded by a total of ___ electron domains and is therefore ___ -hybridized. There is ___ unhybridized porbital on the B atom, which contains no electrons. (Do NOT enter any special formatting for the hybridization.)

3, sp2, 1

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.)

90, 120

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.

Match each substance correctly to the principal type(s) of intermolecular force(s) present, other than covalent bonding. Instructions

CH3OH - hydrogen bonding CH3F - dipole dipole forces C3H8 - dispersion forces CaCl2 - ionic bonding

Which of the following statements correctly describe valence bond theory? Select all that apply.

The space formed by overlapping orbitals can accommodate a maximum of two electrons. The overlap of orbitals to form a bond results in a lower potential energy for the system. A covalent bond results from the attraction between the nuclei of the two bonded atoms and the shared electron pair.

Select all the statements that correctly describe the bonding and geometry in the polyatomic ion SeCl5-.

There are 6 electron domains around the central atom. There is one lone pair on the central atom. The molecular geometry is square pyramidal.

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.

According to valence bond theory, a(n) _____ bond is formed by the overlap of orbitals from two atoms. Energy is released during this process so that the system is at a _____ potential energy after bonding.

covalent, lower

Which intermolecular forces are exhibited between molecules of the compound shown? Select all that apply.

Dipole-dipole forces Dispersion forces

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.

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

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

Draw the Lewis structures for NH2-, NH3, and NH4+. How would you expect the H-N-H bond angle in each species to compare?

NH2- < NH3 < NH4+

In the molecule KrBr2 there are _______electron domains surrounding the central Kr atom; _______bonding pair(s) and lone pair(s). The molecular geometry around the central atom is therefore ______.

5, 2, 3, linear

Match each ideal bond angle with the correct electron-domain geometry in each case.

90 - octahedral 120 - trigonal planar 109.5 - tetrahedral 180- linear 90 and 120 - trigonal bipyramidal

Molecular shapes can be classified using the general designation ABx. Match each symbol in this designation with its correct meaning.

A - central atom in structure B - terminal atom x - number of terminal atoms

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

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

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

lone, bond

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 by applying the VSEPR model 4. Determine the molecular shape by considering the positions of the atoms only.

The Lewis structure for one of the resonance forms of the sulfate ion, SO(4)2-, is shown. What is the approximate value of the marked O-S-O bond angle?

109.5

Select all the statements that correctly explain why lone pairs prefer to occupy equatorial positions in a system with five electron domains.

A lone pair in an equatorial position has more space. There is less repulsion between electron domains in equatorial positions.

Which of the following statements correctly describe the VSEPR model? Select all that apply.

According to this model, the valence electrons around a central atom are located as far from each other as possible. The VSEPR model is used to predict the geometry of a covalently bonded species. A Lewis structure is necessary in order to apply the VSEPR model.

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

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. Use the molecular formula to draw the Lewis structure.

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 number of electron domains with the correct electron-domain geometry. Instructions

Linear - 2 Trigonal planar - 3 Tetrahedral - 4 Trigonal bipyramidal - 5 Octahedral - 6

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. 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.

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

Which position will a lone pair preferentially occupy in a trigonal bipyramidal geometry and why?

The equatorial position because it affords more separation from other domains for the greater repulsion of a lone pair.

Which of the following statements correctly explain why hydrogen bonding requires that H should be covalently bonded to N, O, or F? Select all that apply.

These elements are small, allowing their lone pairs to approach the H of an adjacent molecule closely. N, O, and F are so electronegative that a H covalently bonded to any one of these elements has very high positive character.