CH 9 Bonding & Molecular Structure: Fundamental Concepts

If two or more molecules or ions have the same number of electrons and the same Lewis structure, they are said to be ________. a) covalent b) resonant structures c) neutral d) alkanes e) isoelectronic

E) isoelectronic

In PCl5, the equatorial chlorine atoms have Cl-P-Cl bond angles equal to ____ degrees.

120

What is the total number of valence electrons in a carbon tetrachloride molecule?

32

What is the total number of valence electrons in a dinitrogen tetraoxide molecule?

34

In the Lewis structure for dinitrogen tetraoxide, how many lone pairs of electrons surround the each nitrogen atom? a) 0 b) 1/2 c) 1 d) 2 e) 4

A) 0

How many lone pairs of electrons are on the sulfur atom in SO2? a) 1 b) 2 c) 3 d) 4 e) none

A) 1

Which of the following elements is most likely to form a molecule that does not obey the octet rule? a) B b) C c) N d) O e) F

A) B

Which of the following species will have a Lewis structure most like that of ammonia, NH3? a) H3O+ b) SO3 c) NO3- d) IO3 e) CO32-

A) H3O+

For a main group element, the number of valence electrons is a) equal to the group number. b) equal to eight minus the group number. c) equal to the period number. d) the number of core electrons. e) the principle quantum number

A) equal to the group number

Which of the following molecules or ions have a dipole moment: ICl2-, PF6-, BrF5, and SO42-? a) BrF5 only 2- b) BrF5 and SO4 c) PF6-, BrF5 and SO42- d) ICl2- and BrF5 e) ICl2- and PF6-

A)BrF5 only 2-

What is the expected number of valence electrons for a group 3A element? a) 0 b) 3 c) 5 d) 6 e) 10

B) 3

The central atom in SF4 is surrounded by a) 4 single bonds, no double bonds, and no lone pairs of electrons. b) 4 single bonds, no double bonds, and 1 lo ne pairs of electrons. c) 3 single bonds, 1 double bond, and 1 lone pair of electrons. d) 2 single bonds, 2 double bonds, and no lone pairs of electrons. e) no single bonds, 4 double bonds, and 2 lone pairs of electrons.

B) 4 single bonds, no double bonds, and 1 lo ne pairs of electrons.

The central atom in BrF5 is surrounded by a) 5 single bonds, no double bonds, and no lone pairs of electrons. b) 5 single bonds, no double bonds, and 1 lone pair of electrons. c) 4 single bonds, 1 double bond, and no lone pairs of electrons. d) 3 single bonds, 2 double bonds, and no lone pairs of electrons. e) 2 single bonds, 2 double bonds, and 2 lone pairs of electrons.

B) 5 single bonds, no double bonds, and 1 lone pair of electrons.

Which of the following combinations is most likely to produce ionic bonds? a) O and H b) Al and S c) C and N d) N and O e) S and Cl

B) Al and S

Which statement concerning the relationship between bond order, bond length, and bond energy is correct? a) As bond order increases, both bond length and bond energy increase. b) As bond order increases, bond length is unchanged, bond energy increases. c) As bond order increases, bond length decreases and bond energy increases. d) As bond order increases, bond length increases and bond energy is unchanged. e) As bond order increases, both bond length and bond energy decrease.

C) As bond order increases, bond length decreases and bond energy increases.

52. Which of the following molecules have a dipole moment: CHCl3, NH2Br, NH3, and BH3? a) NH3 and BH3 b) CHCl3 only c) CHCl3, NH2Br, and NH3 d) CHCl3 and NH2Br e) CHCl3, NH2Br, NH3, and BH3

C) CHCl3, NH2Br, and NH3

Which of the following molecules or ions are free radicals: N2O, NO, OCl-, SO2+, and H3O+? a) N2O and H3O+ b) N2O and NO c) NO and SO2+ d) OCl- and SO2+ e) all of the above

C) NO and SO2+

What is the formal charge on each atom in the hypochlorite ion, OCl-? a) O = +1, Cl = -2 b) O = 0, Cl = -1 c) O = -1, Cl = 0 d) O = -1, Cl = +1 e) O = -2, Cl = +1

C) O = -1, Cl = 0

When bonding electrons are unequally shared, we say that the bond is polar. Linus Pauling noticed that the energy of a polar bond is often greater than expected. He attributed the greater bond energy to a) the higher number of valence electrons found in heteronuclear bonds. b) the greater bond lengths of the heteronuclear bonds. c) a coulombic attraction between the partially positive and negative charged atoms. d) one of the many unexplainable phenomena that scientists encounter. e) the ability of heteronuclear species to form double and triple bonds.

C) a coulombic attraction between the partially positive and negative charged atoms.

When both of the electrons in a molecular bond originate from the same atom, the bond is called a(n) a) ionic bond. b) free radical bond .c) coordinate covalent bond. d) Lewis dot structure. e) double bond

C) coordinate covalent bond

Predict which of the following compounds will have the bond that is most polar. a) NH3 b) CF4 c) H2O d) HF e) HI

D) CF4

Which of the following compounds would be expected to have the strongest ionic bonds? a) SrO b) RbI c) NaBr d) MgO e) BaS

D) MgO

Which of the following species will have a Lewis structure most like that of carbon disulfide, CS2? a) NO2 b) SO2 c) H2O d) NO2 e) SF2

D) NO2

Which of the following elements is most likely to form a molecule that exceeds the octet rule? a) Ne b) C c) O d) P e) Be

D) P

Pure covalent bonds, ones where the bonding electrons are shared equally between two atoms, only exist for a) period 2 nonmetals. b) group 4A nonmetals. c) metals. d) bonds between two identical atoms. e) ionic compounds.

D) bonds between two identical atoms

Which of the following statements is incorrect? a) Bond energies can be used to estimates heats of reaction. b) Bond dissociation energies increase with increasing bond order. c) Bond dissociation energies are calculated for substances in the gas phase. d) Bond energies of a given type (e.g. C-H bonds) vary slightly between molecules. e) Bond dissociation energies are always exothermic.

E) Bond dissociation energies are always exothermic.

Which of the following species will have a Lewis structure most like that of thiosulfate ion, S2O32-? a) XeF4 b) SF4 c) ICl4 d) SO3 e) IO4

E) IO4

Which of the following compounds would be expected to have the strongest ionic bonds? a) KI b) NaBr c) NaI d) CsF e) LiF

E) LiF

Which of the following molecules or ions are isoelectronic: O2, N2, CN-, CO, and F2? a) O2, CN-, and F2 b) O2, N2, and F2 c) N2 and F2 d) O2 and CO e) N2, CN-, and CO

E) N2, CN-, and CO

Place the following molecules in order from smallest to largest bond angles: CCl4, NH3, and NH2-. a)CCl4 <NH3-<NH2 b) CCl4 < NH2 < NH3 c)NH3-<NH2- <CCl4 d) NH2- < CCl4 < NH3 e) NH2 < NH3 < CCl4

E) NH2 < NH3 < CCl4

Electronegativity is a measure of a) the charge on an electron. b) a molecule's polarity. c) the charge on an atom. d) the number of extra electrons on an anion. e) an atom's ability to attract electrons to itself.

E) an atom's ability to attract electrons to itself

A molecule has a trigonal bipyramidal electron geometry and a see-saw molecular geometry. Is the lone pair of electrons occupying an equatorial or an axial position? Explain your answer.

The lone pair is in an equatorial position. The equatorial position has the greatest separation between the lone pair and the bonding electrons.

60. The second ionization energy of potassium is much greater than that of calcium. Explain.

Valence shell electrons are more easily removed than inner shell electrons. The first ionization of potassium removes the only electron which occupies the fourth shell. The second ionization of potassium requires removal of an electron from an inner shell. For calcium, both the first and second ionizations remove electrons in the outermost shell.

If a molecule has a positive and a negative end, the molecule is said to have a ________.

dipole

The ________ energy is the energy of formation of one mole of a solid crystalline ionic compound from gas phase ions.

lattice

Three equivalent Lewis structures can be drawn for SO3. Each structure consists of two single sulfur-oxygen bonds and one double bond. These three equivalent structures are referred to as ________ structures.

resonance

The molecular geometry of a molecule whose central atom has four single bonds and two lone pairs of electrons is ________.

square planar