Gen Chem One - Exam 3 (ch9-11)

A group of sp3 hybrid orbitals is formed by the hybridization of ___ s and ___ p orbital(s) from the valence shell of an atom. These hybrid orbitals have the same ___ and energy.

1, 3, geometry

It is possible for two covalently bonded atoms to share more than one electron pair. For example, in a double bond there are _____ shared electron pairs, making a total of _____ shared electrons, and the bond order is _____.

2,4,2

Valence bond theory

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

Why is BeF2 a nonpolar molecule? A. BeF2 is linear and therefore the individual bond dipoles cancel to give no net dipole. B. The individual bonds in BeF2 are nonpolar so the molecule is nonpolar. C. BeF2 contains polar bonds but is unsymmetrical in shape, which makes it nonpolar.

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

In general, the formation of a bond between two or more atoms ______. (Select all that apply.) A. decreases both kinetic and potential energy B. produces a more stable system C. lowers the potential energy between oppositely charge particles D. increases the overall potential energy of the system

produces a more stable system, lowers the potential energy between oppositely charge particles

In a single, double, or triple bond, the shared electron pairs are localized between the bonded atoms. In a resonance hybrid, electrons are ___ or spread out over two or more adjacent atoms. Instead of a double or triple bond between two such atoms, the bond is considered a(n) ___ double or triple bond with a fractional bond order.

shared, partial

Consider the molecule CCl4. Each C-Cl bond in this molecule is ___ because the electronegativity difference between C and Cl is ___ than 0.4. Since CCl4 is tetrahedral in shape and symmetrical, the individual bond dipoles ___ and the molecule is ___ overall.

polar, greater, balance, non polar

Molecular orbitals formed from the combination of atomic s orbitals are called ___ molecular orbitals because they are cylindrically symmetrical. The molecular orbitals formed from atomic 1s orbitals are designated σ for the ___ molecular orbital and σ1s for the ___ molecular orbital.

sigma, anti-bonding, bonding

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 end-to-end combination of a pair of atomic p orbitals gives a pair of _____ molecular orbitals (MOs), whereas side-to-side combination produces a pair of _____ molecular orbitals. A group of three atomic p orbitals will always give rise to _____ pair(s) of π MOs and _____ pair(s) of σ MOs.

sigma, pi, 2, 1

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 empty

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 ___ to the remaining unhybridized p orbital.

sp^2, trigonal, 90

Molecular polarity has a direct effect on the behavior of molecular compounds. The attractive forces between polar molecules are _____ than those between nonpolar molecules. It therefore takes _____ energy to separate polar molecules from each other, and a polar compound will have a _____ boiling point than a nonpolar compound of similar size.

stronger, more, higher

intermolecular forces

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

A molecule that contains covalent bonds and has a(n) ___ arrangement of electron groups will have an overall ___ polarity, which is measured as a dipole ___.

unequal, molecular, moment

The simplest model used to describe the bonding in metals is the electron-sea model. In terms of this model, all the metal atoms contribute their ___ electrons to form an electron "sea" so that the electrons are ___ or shared among all the atoms. The metal is held together by the attraction between the metal ___ and the sea of electrons.

valence, distributed, ions

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, addition, subtraction

Which of the following statements correctly describe the general principles of molecular orbital theory? Select all that apply. A. Bonding involves the overlap of hybrid orbitals. B. Bonding involves the addition and subtraction of wave functions. C. Orbitals are viewed as wave functions. D. The addition of two wave functions produces a region with increased electron density. E. Two atomic orbitals combine to produce a single molecular orbital.

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

Which of the following options correctly describe electronegativity? Select all that apply. A. Electronegativity measures the ability of an atom in a covalent bond to attract the shared electron pair(s). B. Electronegativity can be measured by measuring the energy changes when an atom gains an electron. C. Electronegativity is another word for electron affinity. D. The most electronegative element is hydrogen because it has the smallest atomic size. E. Electronegativity is a relative quantity.

Electronegativity measures the ability of an atom in a covalent bond to attract the shared electron pair(s), Electronegativity is a relative quantity.

True or false: A molecular covalent substance (such as CO2) has a low melting point because the covalent bonds that hold the molecules together are weak and do not require much energy to break.

False: Covalent bonds are strong and require a great deal of energy to break. When a molecular covalent substance melts, it is not the covalent bonds that break, but rather the intermolecular forces between the separate molecules. Since these forces are weak, they require much less energy to break.

σ2p orbital

Formed by end-to-end combination of atomic 2p orbitals

π2p orbital

Formed by side-to-side combination of atomic 2p orbitals

Which of the following statements correctly describe a covalent bond? Select all that apply. A. In a stable covalent bond, nucleus-electron attractions dominate the system. B. A covalent bond results from the attraction between the electrons of two different atoms. C. Formation of a covalent bond results in increased electron density between the two nuclei. D. If the two atoms in a covalent bond approach too closely, the system will become less stable. E. As two atoms form a covalent bond, the energy of the system increases.

In a stable covalent bond, nucleus-electron attractions dominate the system, Formation of a covalent bond results in increased electron density between the two nuclei, If the two atoms in a covalent bond approach too closely, the system will become less stable.

Which of the following options correctly defines resonance structures? A. Lewis structures that contain multiple bonds B. Lewis structures that have the same molecular formula but a different placement of atoms C. Lewis structures for the same species that differ in the placement of electrons D. Lewis structures for the same species that have a different total number of electrons

Lewis structures for the same species that differ in the placement of electrons

Select the correct statements describing molecular covalent solids. Select all that apply. A. Molecular covalent solids have very high melting and boiling points. B. Molecular covalent solids are always hard. C. Molecular covalent solids have intermolecular forces between molecules. D. Molecular covalent solids have low melting and boiling points E. Molecular covalent solids are either soft or hard but brittle.

Molecular covalent solids have intermolecular forces between molecules, Molecular covalent solids have low melting and boiling points, Molecular covalent solids are either soft or hard but brittle.

Which of the following options correctly describe the hybridization of s, p, and d orbitals? Select all that apply. A. Only elements from Period 3 onward can use d orbitals for bonding. B. An atom that has an octahedral geometry is sp3d hybridized. C. The hybridization of an atom surrounded by six electron pairs is sp3d2. D. An atom surrounded by five electron pairs will exhibit sp3d2 hybridization.

Only elements from Period 3 onward can use d orbitals for bonding, The hybridization of an atom surrounded by six electron pairs is sp3d2.

Which of the following properties is common to BOTH molecular covalent substances and network covalent substances? A. Low solubility in water B. Poor electrical conductivity in any phase C. Solids tend to be hard but brittle D. Very high melting points

Poor electrical conductivity in any phase

Which of the following statements correctly describe a σ bond? Select all that apply. A. Single bonds are σ bonds. B. A σ bond concentrates electron density above and below the plane of the two bonded atoms. C. A σ bond can only result from the overlap of p orbitals. D. A σ bond results from end-to-end overlap of two orbitals.

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

σ2p

Single region of high electron density between bonded nuclei

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

π2p

Two separate regions of high electron density between nuclei, above and below bond axis

σ∗2p and π2

Zero electron density between bonded nuclei

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.

amount, 1, 2

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

The bond formed between two nonmetal atoms is called a(n) ___bond. This type of bond arises from the net attraction between the ___ of each atom and the electrons of the other, and results in electrons being ___ between the two atoms.

covalent, nucleus, shared

A central atom can be surrounded by five or six electron groups if ___ orbitals are available for bonding. The appropriate number of equivalent bonding orbitals is formed by combining ___ s orbital(s), ___ p orbital(s), and one or two ___ orbitals.

d, 1, 3, d

The polarity of a molecule can be expressed in terms of its moment (symbol μ), which is the product of the partial in the molecule and the between their centers.

dipole, charges, distance

The relative ability of a bonded atom to attract shared electron pairs is called its _____. This ability _____ as the size of the atom decreases because for a smaller atom the shared electrons will be closer to the nucleus.

electronegativity, increases

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.

hybridized, shared

A molecular orbital is a region of space in a covalent species where electrons are likely to be found. 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

A polar bond is a covalent bond in which there is an electronegativity difference between the two bonded atoms and electrons are shared unequally. The atom with the higher electronegativity will have a partial _____ charge and is marked with the symbol _____ while the atom with the lower electronegativity will have a partial _____ charge and is marked with the symbol _____.

negative; δ-, positive; δ+

Consider the combination of two atomic orbitals to form a pair of molecular orbitals, designated σ2s and σ∗2s. Which of the following statements explain these designations correctly? A. The orbital designated σ*2s is the bonding molecular orbital B. The atomic orbitals that combine in this case are s orbitals. C. The subscript "2" indicates the number of atomic orbitals that combine to form each molecular orbital. D. Both orbitals are designated σ because they are cylindrically symmetrical.

The atomic orbitals that combine in this case are s orbitals, Both orbitals are designated σ because they are cylindrically symmetrical.

Select the statement that correctly explains the source of the energy change in a chemical reaction. A. The enthalpy of a reaction is largely due to changes in the kinetic energy of the reactants and products. B. The main contribution to ΔH is from increased or decreased repulsions between electrons. C. The main contribution to ΔH is the difference in the bond energies of reactants and products. D. The energy absorbed or released in a reaction is due to changes in the nuclei of the atoms.

The main contribution to ΔH is the difference in the bond energies of reactants and products.

Select all the statements that correctly describe the electron-sea model of metallic bonding. A. The valence electrons of the bonded atoms are shared in an electron sea. B. Each metal atom shares a pair of electrons with the metal atoms on either side. C. The metal "cations" are held very rigidly in place to form a brittle three-dimensional lattice. D. Two or more metals can combine to form alloys of variable composition by sharing their valence electrons.

The valence electrons of the bonded atoms are shared in an electron sea, Two or more metals can combine to form alloys of variable composition by sharing their valence electrons.

The enthalpy of a reaction, ΔHrxn, is the overall heat change resulting from ______ energies when reactant bonds break and ______ energies when product bonds form.

absorbing, releasing

Which of the following statements correctly describe a polar covalent bond? Select all that apply. A. A polar bond is a covalent bond in which electrons are shared equally. B. In a polar covalent bond the atom with the lower electronegativity is marked δ- because it has less electron density. C. A bond between atoms whose electronegativities differ by more than 0.4 but less than 1.7 is polar. D. In a polar covalent bond the electron density is highest over the more electronegative atom.

A bond between atoms whose electronegativities differ by more than 0.4 but less than 1.7 is polar, In a polar covalent bond the electron density is highest over the more electronegative atom.

Which of the following statements correctly describe bonding and antibonding molecular orbitals? Select all that apply. A. A bonding molecular orbital is lower in energy than the original atomic orbitals. B. A bonding molecular orbital has a region of very low electron density between the nuclei of the bonding atoms. C. A bonding molecular orbital is formed by the addition of the wave functions for two atomic orbitals. D. An antibonding molecular orbital has a region of zero electron density between the nuclei of the bonding atoms. D. The node of an orbital is an area of high electron density.

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.

Molecular orbital theory

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

Which of the following statements correctly describe the effect of molecular polarity on the behavior of a molecular compound? Select all that apply. A. A polar compound will experience stronger intermolecular forces than a nonpolar compound. B. The physical properties of a molecular compound are directly related to molecular polarity. C. Polar and nonpolar molecules have very similar physical properties. D. Polar molecules exhibit the properties of ionic compounds because they contain partial charges.

A polar compound will experience stronger intermolecular forces than a nonpolar compound, The physical properties of a molecular compound are directly related to molecular polarity.

Which of the following statements correctly describe resonance structures? Select all that apply. A. Resonance forms rapidly interconvert. The species could have any one of these structures at any time. B. An individual resonance structure does not accurately represent the structure of the species. C. Resonance structures differ only in the arrangement of electrons. D. Resonance structures are isomers of the same species.

An individual resonance structure does not accurately represent the structure of the species, Resonance structures differ only in the arrangement of electrons.

Which of the following statements correctly describe sp3 hybrid orbitals? Select all that apply. A. The four sp3 hybrid orbitals are lower in energy than the original atomic orbitals from which they were formed. B. An sp3 hybrid orbital is unsymmetrical in shape, having one small and one large lobe. C. The four sp3 hybrid orbitals of a group are equivalent in shape and energy. D. The sp3 hybrid orbitals are perpendicular to each other.

An sp3 hybrid orbital is unsymmetrical in shape, having one small and one large lobe, The four sp3 hybrid orbitals of a group are equivalent in shape and energy.

Which of the following options correctly describe σ and π molecular orbitals? Select all that apply. A. Atomic p orbitals can combine to form either σ or π molecular orbitals. B. A π* molecular orbital has a region of high electron density between the bonding nuclei. C. A π bonding molecular orbital is usually lower in energy than a σ bonding molecular orbital. D. A π bonding molecular orbital has two regions of high electron density. E. Both atomic s and p orbitals can form σ molecular orbitals.

Atomic p orbitals can combine to form either σ or π molecular orbitals, A π bonding molecular orbital has two regions of high electron density, Both atomic s and p orbitals can form σ molecular orbitals.

Which of the following statements correctly describe how to determine whether a given molecule is polar or nonpolar? Select all that apply. A. For a molecule that has polar bonds, the geometry must be known in order to predict the overall polarity. B. A molecule that has a symmetrical geometry is always nonpolar. C. If the individual bond dipoles do not cancel, the molecule is polar. D. If a molecule contains no dipole moments across any bonds, it will be 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 sp hybrid orbitals? Select all that apply. A. An sp-hybridized atom has one unhybridized p orbital in its valence shell. B. The angle between two sp hybrid orbitals is 90o. C. The combination of one s and one p orbital results in the formation of one sp hybrid orbital. D. The energy of an sp hybrid orbital lies between the energies of the original s and p orbital that were mixed. E. 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, Each sp hybrid orbital has one large and one small lobe.

Which of the following statements correctly describe the formation of sp2 hybrid orbitals? Select all that apply. A. An sp2 hybrid orbital is identical to an sp hybrid orbital in shape and energy. B. The formation of sp2 hybrid orbitals leaves one unhybridized valence p orbital. C. Three sp2 hybrid orbitals are formed by the hybridization of one s and one p orbital. D. A group of sp2 hybrid orbitals assumes a trigonal planar geometry.

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 options correctly explain the differences in physical behavior of molecular covalent substances and network covalent substances? Select all that apply. A. The relatively low boiling points of molecular substances reflect the strength of the intermolecular forces between the individual molecules. B. Molecular covalent substances melt at low temperatures because their covalent bonds are easy to break. C. The strong covalent bonds that hold the atoms of a network covalent substance together require a lot of energy to break. D. Network covalent substances have high melting points because their particles are held together by strong ionic bonds.

The relatively low boiling points of molecular substances reflect the strength of the intermolecular forces between the individual molecules, The strong covalent bonds that hold the atoms of a network covalent substance together require a lot of energy to break.