Chemistry - Chapter 11 Theories of Covalent Bonding

Which of the following statements correctly describe bonding and antibonding molecular orbitals?

A bonding molecular orbital is lower in energy than the original atomic orbitals A bonding molecular orbital is formed by the addition of the wave functions for two atomic orbitals An antibonding molecular orbital has a region of zero electron density between the nuclei of the bonding atoms

Which of the following statements correctly describes how Pauling's hybridization model explains differences between the geometry of atomic orbitals and observed bond angles?

Valence orbitals of the atoms mix to become new hybrid orbitals in the molecule The spatial orientations of hybrid orbitals match the observed molecular shapes

Valence bond theory describes a single covalent bond as the _____ of orbitals from two atoms to form a shared space, which is occupied by _____ electron(s).

overlap ; two

A bond formed by sideways overlap of two p orbitals (one from each bonding atom) is called a(n) _____ bond. This type of bond has _____ regions of electron density.

pi ; two

A bond formed by the overlap of two s orbitals or the end-to-end overlap of two orbitals that have p character is called a(n) ____ bond. This bond has its highest electron density between the ____ of the two bonded atoms.

sigma ; nuclei

The hybridization of one s and one p orbital will result in the formation of two _____ hybrid orbitals. This will leave _____ unhybridized valence p orbital(s), lying at right angles to the hybrid orbitals.

sp ; two

A π bond is ______ than a σ bond because it involves a _____ degree of orbital overlap.

weaker ; lesser

Molecular Orbital Theory

A molecule is seen as a collection of nuclei with orbitals delocalized over the whole molecule

Valence Bond Theory

Atoms are bonded through localized overlap of half-filled, hybridized, valence-shell atomic orbitals

Which of the following options correctly describe sp hybrid orbitals?

Each sp hybrid orbital has one large and one small lobe The energy of an sp hybrid orbital lies between the energies of the original s and p orbital that were mixed

A double bond is ______ a single bond because the strength of the π bond component is ______ that of the σ bond component.

less than twice as strong as ; weaker than

The combination of two atomic orbitals always forms two molecular orbitals; the bonding molecular orbital, which is _____ in energy, and the antibonding molecular orbital, which is _____ in energy, than the original atomic orbitals.

lower ; higher

Hybrid orbitals are designated by using a superscript to indicate the ____ of each type of orbital used to form them. For example, the designation sp2 indicates that ____ s and ____ p orbital(s) were combined to form this orbital type.

number ; one ; two

The combination of one s and two p orbitals will form a group of three ____ hybrid orbitals. These hybrid orbitals adopt a(n) ____ planar geometry and are at an angle of ____ degrees to the remaining unhybridized p orbital.

sp^2 ; trigonal ; 90

Valence bond theory proposes that before a covalent bond forms, atomic orbitals from a given atom can combine to form new atomic orbitals. This process is called _____ of orbitals, and the new atomic orbitals are referred to as ______ orbitals.

Hybridization ; hybrid

Type of hybrid orbitals formed varies with:

The type of atomic orbitals mixed

Valence bond theory describes covalent bonding as the localized overlap of half-filled valence-shell _____ atomic orbitals. Molecular orbital theory, on the other hand, describes a molecule as a collection of nuclei with orbitals _____ over the whole molecule.

hybrid ; extending

A double bond is always made up of _____ σ and _____ π bond(s). A double bond is _____ than a single bond.

one ; one ; stronger

A triple bond is composed of _____ σ and _____ π bond(s).

one ; two

According to the molecular orbital model of covalent bonding, orbitals are viewed as _____ functions. The formation of a bond involves the mathematical combination of these functions, either by _____ to give an area of increased electron density or by ______ to give an area of decreased electron density.

wave ; bonding ; antibonding

Which of the following statements correctly describe a π bond?

A multiple bond always contains at least one π bond A π bond is formed by the side-to-side overlap of two p orbitals

Why is rotation about a π bond restricted?

Free rotation would disrupt the parallel arrangement of the p orbitals, causing the bond to break

Which of the following statements correctly defines hybrid orbitals?

Orbitals used for bonding that are formed by mixing atomic orbitals from the same atom

Which of the following statements correctly describe a σ bond?

Single bonds are σ bonds A σ bond results from end-to-end overlap of two orbitals

Which of the following statements correctly describe the general principles of molecular orbital theory?

The addition of two wave functions produces a region with increased electron density Orbitals are viewed as wave functions Bonding involves the addition and subtraction of wave functions

Which of the following statements correctly describe the formation of sp2 hybrid orbitals?

The formation of sp2 hybrid orbitals leaves one unhybridized valence p orbital A group of sp2 hybrid orbitals assumes a trigonal planar geometry

Which of the following statements correctly describe a covalent bond in terms of valence bond theory?

The greater the overlapped area, the stronger the bond A covalent bond is formed by the overlap of an orbital from each of the bonding atoms The electrons of a shared pair must have opposite spins

The number of hybrid orbitals formed equals:

The number of atomic orbitals mixed

A particular hybrid orbital is designated sp3d2. What information is provided by the superscripts in this designation?

The number of each type of atomic orbital combined to produce this type of hybrid orbital

Why is the hybridization model necessary to explain the bonding in a molecule such as CH4?

The observed bond angles cannot be explained with reference to unhybridized orbitals The atomic electron configuration of carbon cannot account for four equivalent bonds

Shape and orientation of a hybrid orbital maximizes:

The overlap with the other atoms in the bond

A π bond restricts rotation around a bond because it requires the p orbitals to be aligned ______ the axis of the bonded atoms to achieve good overlap.

above and below