CHEM Chapter 10 Chemical bonding II: molecular geometry

Match each type of molecular orbital to the correct description

-Bonding MOs are : lower in energy than the atomic orbitals they are formed from -antibonding MOs are : higher in energy than the atomic orbitals they are formed from

Match each type of orbital hybridization with the corresponding geometry

-sp : linear -sp^2 : trigonal planar -sp^3 : tetrahedral -sp^3d : trigonal bipyramidal -sp^3d^2 : octahedral

Polar bond

A covalent bond in which the shared electron pair is distributed unevenly between the atoms

In a covalent bond between identical atoms, the electrons are shared _________ between the atoms. If the atoms are not identical, the electron distribution is __________ so that the electrons are closer to one atom than the other. This type of bond is called a(n) _______ covalent bond

Equally; unequal; polar

A bond formed by the sideways overlap of two p orbitals is called a _________ bond. This type of bond is _______ than the bond formed by end-to-end orbital overlap

Pi; weaker

Consider the molecule CCl4. Each C-Cl bond in this molecule is ______ because Cl and C have different electronegativities. Since CCl4 is tetrahedra in geometry and symmetrical, the individual bond dipoles ______ and the molecule is _________ overall

Polar; cancel; nonpolar

The molecule CHCl2 is __________ in shape

Tetrahedral

The hybrid orbitals of a specific group -are equal in energy -are lower in energy than all the atomic orbitals used to form them -have the same shape -are formed by mixing all the valence-shell atomic orbitals

-are equal in energy -have the same shape

Which of the following statements correctly describe a pi bond? -a pi bond is formed by the side-to-side overlap of two p orbitals -a pi bond concentrates electron density along the axis between two nuclei -a pi bond holds two electrons, one in each region of the bond -a multiple bond always contains at least one pi bond

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

Match each type of molecular orbital with the correct description of its electron density

-(sigma)2p : single region of high electron density between bonded nuclei -(sigma)*2p and (pi)*2p : zero electron density between bonded nuclei -(pi)2p: two separate regions of high electron density between the nuclei, above and below

When drawing a molecular orbital diagram _________ -one electron is placed in each MO of equal energy before electrons are paired up -one electron is placed in each sigma MO before electrons are paired up -a lower energy orbital is filled before electrons are placed in a higher energy orbital -all bonding MOs are filled before electrons are placed in antibonding MOs

-One electron is placed in each MO of equal energy before electrons are paired up -a lower energy orbital is filled before electrons are placed in a higher energy orbital

Hybrid orbitals ________

-are formed by the mixing of atomic orbitals from the same atom -are equivalent in energy -adopt the geometry predicted for a given atom using VSEPR

Match each molecular geometry with the correct general formula

-linear : AB2 -trigonal planar: AB3 -tetrahedral : AB4 -trigonal bipyramidal : AB5 -octahedral : AB6

Which of the following statements correctly describe a covalent bond in terms of valence bond theory? -the space shared by two orbitals between the atoms can contain up to 3 shared electrons -substantial overlap of atomic orbitals results in the formation of a stable molecule -the formation of a covalent bond results in an increase in potential energy -a covalent bond is formed by the overlap of an orbital from each of the bonding atoms

-substantial overlap of atomic orbitals results in the formation of a stable molecule -formed by the overlap of an orbital from each of the bonding atoms

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

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

Which of the following options correctly describe a dipole moment> -the term "dipole moment" only applies to individual bonds, not to molecules -the dipole moment provides a quantitative measure of bond polarity -a dipole moment indicates that a molecule contains charged atoms -a dipole moment arises when a bond or a molecule has an uneven distribution of electron density

-the dipole moment provides a quantitative measure of bond polarity -a dipole moment arises when a bond or a molecule has an uneven distribution of electron density

Elements from period _____ onward can have more than 4 valence electron groups. To do so, _______ orbitals would be mixed with the valence-shell s and p orbitals to provide enough hybrid orbitals to accommodate these electrons groups

3; d orbitals from the same valence shell

Molecular bond order is calculated from an MO diagram by subtracting the number of electrons in _______ orbitals from the number of electrons in ______ orbitals then dividing by 2.

Anti bonding; bonding

Valence bond theory assumes that electrons in a molecule occupy _______ orbitals of the individual atoms. Conversely, molecular orbital theory describes bonding in terms of the interaction of atomic orbitals to form _________ orbitals that are associated with the entire covalent species.

Atomic; molecular

To classify geometry, a structure is assigned a specific ABx designation, where A is the ________ atom, B is a different element bonded to A, and x is an integer from 2 to ____.

Central; 6

_________ molecular orbitals are not confined between two adjacent bonding atoms but are extended over three or more atoms.

Delocalized

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

A molecule containing polar bonds will be nonpolar overall if ________

Its geometry allows the bond dipoles to cancel

A particular hybrid orbital is designated sp^3d^2. 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

Which of the following determines the geometry around a central atom in a Lewis structure? -the number of lone electron pairs -the number of valence-shell electron pairs -the total number of electrons associated with the central atom -the number of shared electron pairs

The number of valence-shell electron pairs

Why do the energies of the molecular orbitals formed for species O2, F2, and Ne2 differ from those of the molecular orbitals for other period 2 elements?

There is a large energy difference between the 2s and 2p orbitals of O, F, and Ne; therefore, no s-p mixing occurs when molecular orbitals are formed.

Both ________ bond theory and molecular _______ theory are quantum mechanical theories used to describe covalent bond formation and the electronic structure of molecules.

Valence; orbital

According to the VSEPR model, each pair of ________ electrons around a central atom will be located as far away from the others as possible, in order to minimize electron-electron ________

Valence; repulsion

According to the molecular orbital model of covalent bonding, electrons in orbitals have _______ characteristics. The formation of a bonding molecular orbital involves the combination of these waves by _______ interference to give an area of increased electron density, whereas an antibonding molecular orbital is formed by ___________ interference to give an area of decreased electron density.

Wave; constructive; destructive

The lower the molecular orbital bond order, the ________ the bond and the ________ stable the species.

Weaker; less

When should the VSEPR model and hybridization theory be applied to describe bonding?

Whenever VSEPR theory and orbital hybridization correctly predict molecular shape

Lone pairs are associated with _____ atom(s) giving them _________ spatial distribution than bonding electrons. For this reason, lone pairs experience greater repulsion from neighboring lone pairs and bonding pairs

One; more

A triple bond is composed of ______ sigma and ______ pi bond(s)

One; two

Which of the following statements correctly defines hybrid orbitals?

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

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 the angle between any two of them is ______ degrees.

Sp2; trigonal; 120

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

The smaller the bond angle, the _______ the electron repulsions for the electron pairs concerned. In a 5-electron pair system, lone pairs prefer to occupy ________ positions because equatorial-equatorial repulsions are ______ than axial-equatorial repulsions

Stronger; equatorial; weaker

Place the steps for determining the geometry of a covalently bonded precise in the correct order.

1. Draw the Lewis structure of the molecule, considering only the electron pairs around the central atom 2. Count the total number of electron pairs around the central atom 3. Predict the geometry of the molecule 4. Predict the bond angles in the molecule

Which of the following options correctly contrast the valence bond (VB) model and the molecular orbital (MO) model of bonding? -VB theory describes bonding as the localized overlap of atomic orbitals -MO theory postulates that the formation of orbitals that are shared by all atoms in covalent species -MO theory cannot account for observed molecular geometries -VB theory rationalizes the geometries predicted using VSEPR -MO theory describes bonding in terms fo hybridization of atomic orbitals

-VB theory describes bonding as the localized overlap of atomic orbitals -MO theory postulates that the formation of orbitals that are shared by all atoms in covalent species -MO theory describes bonding in terms fo hybridization of atomic orbitals

In order to determine whether a molecule is polar or nonpolar _________ -a Lewis structure is typically needed -the polarity of individual bonds should be determined by comparing the electronegativities of the bonded atoms -the Lewis structure can be used for prediction without determining the shape -as long as the molecule has 2 identical bonds it will be nonpolar -any molecule with one or more lone pairs will be polar

-a Lewis structure is typically needed -the polarity of individual bonds should be determined by comparing the electronegativities of the bonded atoms

Which of the following statements correctly describe molecular orbital bond orders? -an increase in the number of antibonding electrons will cause the molecular orbital bond order to increase -the higher the molecular orbital bond order, the less stable the species -a species with more electrons in bonding than antibonding molecular orbitals will have a positive molecular orbital bond order -the lower the molecular orbital bond order, the weaker the bonds between the atoms of the species

-a species with more electrons in bonding than antibonding molecular orbitals will have a positive molecular orbital bond order -the lower the molecular orbital bond order, the weaker the bonds between the atoms of the species

Which of the following options correctly describe a molecular orbital energy level diagram? -can be used to calculate bond order and predict the stability of a species -shows the relative energy and number of electrons in each molecular orbital -shows only the molecular orbitals for a covalent species -typically includes valence-shell molecular orbitals only -electrons do not fill molecular orbitals in the same way that they fill atomic orbitals

-can be used to calculate bond order and predict the stability of a species -shows the relative energy and number of electrons in each molecular orbital -typically includes valence-shell molecular orbitals only

Which of the following are limitations of Lewis bond theory? -doesn't consider the nature of the atoms that share the bonding electrons -accounts for energy changes in covalent bond formation -gives a comprehensive explanation for why covalent bonds exist -provides no explanation for the differences among covalent bonds

-doesn't consider the nature of the atoms that share the bonding electrons -provides no explanation for the differences among covalent bonds

Which of the following options correctly describe sp hybrid orbitals? -the combination of one s and one p orbital results in the formation of one sp hybrid orbital -each sp hybrid orbital has one large and one small lobe -the angle between two sp hybrid orbitals is 90 degrees -an sp-hybridized atom has one unhybridized p orbital in its valence shell -the energy of an sp hybrid orbital lies between the energies of the original s and p 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 orbitals that were mixed

Which of the following statements correctly describe how to determine whether a given molecule is polar or nonpolar? -for a molecule that has polar bonds, the geometry must be known in order to predict the overall polarity -if the individual bond dipoles do not cancel, the molecule is polar -if a molecule contains no dipole moments across any bonds it will be nonpolar -a molecule that has a symmetrical geometry is always nonpolar

-for a molecule that has polar bonds, the geometry must be known in order to predict the overall polarity -if the individual bond dipoles do not cancel, the molecule is polar -if a molecule contains no dipole moments across any bonds it will be nonpolar

Which of the following options correctly describe the valence-shell electrons of an atom? -are the electrons in a filled outer shell -electrons involved in bonding are always valence electrons -are the electrons in the outermost occupied shell -all valence electrons are involved in bonding

-the electrons involved in bonding are always valence electrons -are the electrons in the outermost occupied shell

Which of the following options correctly describe the hybridization of s, p, and d orbitals? -the hybridization of an atom surrounded by 6 electrons is sp3d2 -only elements from period 3 onward can use d orbitals for bonding -An atom that has an octahedral geometry is sp3d-hybridized -an atom surrounded by 5 electron pairs will exhibit p3d2-hybridization

-the hybridization of an atom surrounded by 6 electrons is sp3d2 -only elements from period 3 onward can use d orbitals for bonding

Which of the following cannot be accounted for using the valence bond model of bonding? -the formation of multiple bonds -the magnetic properties of molecules -the observed geometries of covalently bonded species -the use of an expanded valence shell in some structures

-the magnetic properties of molecules

Which of the following statements correctly describe the bonding in benzene?

-three bonding pi molecular orbitals are formed when six p orbitals combine in benzene -benzene has six electron in bonding pi molecular orbitals

Place the following molecular orbitals in order of decreasing energy species for O2, F2, and Ne2 -(pi)*2p -(sigma)2p -(sigma)*2p -(pi)2p

1. (sigma)*2p 2. (pi)*2p 3. (pi)2p 4. (sigma)2p

Arrange the steps for determining the hybridization of an atom in the correct order.

1. Draw a Lewis structure using the molecular formula 2. Count the number of electron pairs surrounding the central atom 3. From the VSEPR model, deduce the geometry of the molecule 4. Match the appropriate hybrid orbital designation with the correct electron pair arrangement

Order the following repulsive forces from greatest to least. Lone-pair versus bonding-pair repulsion Lone-pair versus lone-pair repulsion Bonding-pair versus bonding-pair repulsion

1. Lone-pair vs lone-pair repulsion 2. Lone-pair vs bonding-pair repulsion 3. Bonding-pair vs bonding-pair repulsion

Why are the terms "axial" and "equatorial" not used to describe the bonds in an octahedral system?

All six bonds are equivalent in an octahedral system

Hybrid orbitals are formed by the combination or "mixing" of _________ orbitals from a specific atom. The number of hybrid orbitals formed is ________ to/than the number of orbitals mixed, and the _______ of hybrid orbital varies according to the specific orbitals mixed

Atomic; equal; number

A central atom can be surrounded by 5 or 6 electron pairs if ____ orbitals are available for bonding. The appropriate number of equivalent bonding orbitals is formed by combining ___ s orbital(s), ____ p orbital(s), and 1 or 2 _____ orbitals

D; one; three; d

Molecular orbitals can be formed by the combination of multiple atomic orbitals, allowing electrons to be _________ or shared between several atoms. The molecular orbital model therefore allows a better description of the bonding in ___________ structures.

Delocalized; resonance

The polarity of a bond can be expressed in terms of its ________ moment, which is the product of the partial charge in the bond and the ______ between the bonded atoms

Dipole; distance

The more stable a bonding molecular orbital, the _______ stable the corresponding antibonding molecular orbital will be.

Less

When using VSEPR to predict shape, multiple bonds and lone pairs take up _______ "space" than single bonds. This may distort the ideal geometry

More

Lone pairs repel other electron pairs ______ strongly than bonding electron pairs do. The presence of lone pairs pushes the bonding electron pairs _______, distorting the ideal geometry and ideal bond angles.

More; closer together

Six electron pairs around a central atom form a(n) ___________ arrangement with bond angles of _____ degrees.

Octahedral; 90