Chem 117 - Exam 3
Coordinate Covalent Bond
A bond formed when one atom donates two electrons to another atom that has a vacant valence orbital.
Polar Covalent Bond
A bond in which the bonding electrons are attracted somewhat more strongly by one atom than by the other.
Ionic bond
A bond that results from a transfer of one or more electrons between atoms.
Sigma Bond
A covalent bond formed by head-on overlap of orbitals in which the shared electrons are centered about the axis between the two nuclei.
Double Bond
A covalent bond formed by sharing four electrons between atoms.
Triple Bond
A covalent bond formed by sharing six electrons between atoms.
Single Bond
A covalent bond formed by sharing two electrons between atoms.
Pi Bond
A covalent bond formed by sideways overlap of orbitals in which shared electrons occupy a region above and below a line connecting the two nuclei.
sp Hybrid Orbital
A hybrid orbital formed by combination of one atomic s orbital with one p orbital.
sp³ Hybrid Orbitals
A hybrid orbital formed by combination of one s and three p atomic orbitals.
sp² Hybrid Orbitals
A hybrid orbital formed by combination of one s and two p atomic orbitals.
Valence Shell Electron Pair Repulsion (VSEPR) Model
A model for predicting the approximate shape of a molecule.
Antibonding Molecular Orbital
A molecular orbital that is higher in energy than the atomic orbitals it is derived from.
Bonding Molecular Orbital
A molecular orbital that is lower in energy than the atomic orbitals it is derived from.
Dipole
A pair of separated electrical charges.
Born-Haber Cycle
A pictorial way of viewing the energy changes in the various steps during formation of an ionic solid from its elements.
Molecular Orbital (MO) Theory
A quantum mechanical description of bonding in which electrons occupy molecular orbitals that belong to the entire molecule rather than to an individual atom.
Valence Bond Theory
A quantum mechanical description of bonding that pictures covalent bond formation as the overlap of two singly occupied atomic orbitals.
Electron-Dot Structure
A representation of a molecule that shows valence electrons as dots; also called a Lewis structure.
Ionic solid
A solid whose constituent particles are ions ordered into a regular three-dimensional arrangement held together by ionic bonds.
Phase
A state of matter.
Paramagnetic
A substance that contains unpaired electrons and is attracted by a magnetic field.
Diamagnetic
A substance that has no unpaired electrons and is weakly repelled by a magnetic field.
Hybrid Atomic Orbital
A wave function derived by combination of atomic wave functions.
Molecular Orbital
A wave function whose square gives the probability of finding an electron within a given region of space in a molecule.
Consider the hybridizations of the different carbon atoms in the molecule shown below. H | H-C(triple bond)C-C-C-H 1 2 3 | H (4 is the other carbon) 25. The bond between the carbon atoms labeled 2 and 3 (see figure above) can be described as between orbitals: A. sp hybrid on C2 and sp2 hybrid on C3 B. sp hybrid on C2 and sp3 hybrid on C3 C. sp3 hybrid on C2 and sp3 hybrid on C3 D. unhybridized p on C2 and unhybridized p on C3 E. sp2 hybrid on C2 and sp2 hybrid on C3
A
Place the following in order of increasing radius: Ca 2+, Cl−, S2− A. Cá⁺ < Cl⁻ < S2⁻ B. Cl⁻ < Cá⁺ < S2⁻ C. S2⁻ < Cl⁻ < Cá⁺ D. Cá⁺ < S2⁻ < Cl⁻ E. Cl⁻ < S2⁻ < Cá⁺
A
Using VSEPR Theory, predict the charge cloud geometry, the molecular shape, and the smallest approximate F-Cl-F bond angle of ClF3. A. trigonal bipyramidal, T-shaped, 90 B. tetrahedral, trigonal planar, 109.5 C. trigonal bipyramidal, trigonal pyramidal, 109.5 D. trigonal bipyramidal, trigonal planar, 120 E. trigonal planar, trigonal planar, 120
A
Resonance Theory
Describes many molecules by drawing two or more electron-dot structures and considering the actual molecule to be a composite of these two structures.
Consider the following orderings. I. S < Cl II. Mg < Ca III. Br < F IV. Li < Li+ Which of these give(s) a correct trend in ionization energy? A. Only I. B. Only II. C. Only III. D. Two of them. E. Three of them.
E
Construct correct Lewis dot structures for the three molecules below. SF4 PF 3 IF 3 I. II. III. Determine which of these molecule(s) (see I-III above) are predicted to be polar. A. I B. II C. III D. two of them E. all three of them
E
For which molecule will the charge cloud geometry be different from the molecular shape? A. LiF B. BeF2 C. BF3 D. CF4 E. NF3
E
Predict the relative order of bond lengths: C-C C-Si C-N C=N C=O A. C-N < C=N < C=O < C-C < C-Si B. C-N < C=O < C=N < C-C < C-Si C. C-C < C-Si < C=N < C=O < C-N D. C=O < C=N < C-N < C-Si < C-C E. C=O < C=N < C-N < C-C < C-Si
E
Use the molecular orbital diagram to figure out the electronic configuration for CN. Which of the following statements is correct? (Use the molecular orbital diagram). Highest Energy σ_*2p π_*2p σ_2p π_2p σ_*2s Lowest Energy σ_2s (* means antibonding) A. CN is diamagnetic. B. CN− is paramagnetic. C. If an electron is removed to give CN+, the bond order increases. D. The ∗ orbital is the highest energy orbital containing an electron in CN E. If an electron is added to give CN−, the bond length decreases.
E
Which description of a pi bond is false? A. involves sideways overlap of orbitals on adjacent atoms B. made by the overlap of unhybridized p-orbitals C. restricts rotation about the bonding axis D. orbital overlap is perpendicular to the bonding axis E. stronger than a sigma bond
E
Which statement about drawing Lewis dot structures is incorrect? A. The element sulfur has six electrons in its Lewis symbol. B. One must add electrons when an anion is made. C. Two pairs of electrons are shared between two nuclei in a double bond. D. Not every element will obey the octet rule. E. Period 3 elements, Na to Ar, are never allowed to exceed the octet rule.
E
Radicals
Elements having unpaired elements in a half-filled orbital.
Expanded Octet
Form more bonds than predicted by the octet rule.
Chiral
Having handedness.
Core Electron
Inner shell electron.
Achiral
Lacking handedness.
What is the geometry for atoms with 2 bonds, 0 lone pairs, and 2 charge clouds?
Linear
Organic Compounds
Molecules that contain carbon atoms bonded together in a chain.
Lone Pair
Non bonding electrons.
Electrostatic Potential Map
Portrays the calculated electron distribution in a molecule.
Delocalized
Spread out over the two oxygen-oxygen bonds.
Electron Deficient
Surrounded by less than eight electrons.
Lines Between Atoms
Term used to indicate covalent bonds.
Electronegativity (EN)
The ability of an atom in a molecule to attract the shared electrons in a covalent bond.
Bond Dissociation Energy (D)
The amount of energy necessary to break a chemical bond in an isolated molecule in the gaseous state.
Ionization Energy (E_i)
The amount of energy necessary to remove the outermost electron from an isolated neutral atom in the gaseous state.
Bond angles
The angle at which two adjacent bonds intersect.
Polarizability
The ease with which a molecule's electron cloud can be distorted by a nearby electric field.
Electron Affinity (E_ea)
The energy change that occurs when an electron is added to an isolated atom in the gaseous state.
Coulomb's Law
The force resulting from the interaction of two electric charges is equal to a constant k times the magnitude of the charges divided by the square of the distance between them.
Ground-State Electron Configuration
The lowest-energy electron configuration of an atom.
Dipole Moment
The measure of net molecular polarity; u = Q x r
Bond Length
The minimum-energy distance between nuclei in a covalent bond.
Effective Nuclear Charge (Z_eff)
The net nuclear charge actually felt by an electron.
Bond Order
The number of electron pairs shared between two bonded atoms.
Shield
Conceal or guard.
List whether the following molecules are polar or nonpolar. CH2Cl2 SF4 CÓ A. polar, nonpolar, nonpolar B. nonpolar, nonpolar, polar C. polar, nonpolar, polar D. polar, polar, nonpolar E. nonpolar, polar, polar
D
Place the following ionic compounds in order from lowest to highest lattice energies. LiCl KCl KI MgO CaO Al2Ǒ A. LiCl < KCl < KI < MgO < CaO < Al2Ǒ B. LiCl < KI < KCl < CaO < MgO < Al2Ǒ C. Al2Ǒ < CaO < MgO < KI < KCl < LiCl D. KI < KCl < LiCl < CaO < MgO < Al2Ǒ E. CaO < MgO < Al2Ǒ < KI < KCl < LiCl
D
Use the molecular orbital diagram to figure out the electronic configuration for C2. The bond orders in C2, C2+, and C2− are Highest Energy σ_*2p π_*2p σ_2p π_2p σ_*2s Lowest Energy σ_2s (* means antibonding) A. 1, 1.5, and 2 B. 2, 1.5, and 1 C. 2, 2.5, and 1.5 D. 2, 1.5, and 2.5 E. 1, 2, and 1
D
Which of the following ions would be paramagnetic? A. K+ B. Al3+ C. Sc3+ D. Tí+ E. Cu+
D
Write the correct Lewis dot structure for CF2S. Which statement correctly describes the structure? A. The structure contains 3 single bonds, 1 double bond, and 2 lone pairs. B. The structure contains 3 single bonds, 1 triple bond, and 8 lone pairs. C. The structure contains 2 single bonds, 1 double bond, and 2 lone pairs. D. The structure contains 2 single bonds, 1 double bond and 8 lone pairs. E. The structure contains 1 single bond, 1 triple bond, and 2 lone pairs.
D
Which of the following compounds can exhibit cis-trans isomerism? A. H2C=CH2 B. H2FC-CH2F C. HFC=CHF D. H2C=CFBr E. H2C=O
C
Which of the following molecules is paramagnetic? (Use the molecular orbital diagram) Highest Energy σ_*2p π_*2p σ_2p π_2p σ_*2s Lowest Energy σ_2s (* means antibonding) A. Lí B. Bé C. B2 D. C2 E. N2
C
Which statement is false? A. Na is larger than Na+ B. Mg2+ is smaller than Cá+ C. Br is smaller than Br D. F is smaller than Ó E. P3 is larger than Cl
C
Van Der Waals Forces
An alternative name for intermolecular forces.
Intermolecular Force
An attractive interaction between molecules.
Hydrogen Bond
An attractive intermolecular force between a hydrogen atom bonded to an electronegative O, N, or F atom and an unshared electron pair on a nearby electronegative atom.
Resonance Hybrid
An average of several valid electron-dot structures for a molecule.
Formal Charge
An electron bookkeeping device that tells whether an atom in a molecule has gained or lost electrons compared to an isolated atom.
Schrödinger Wave Equation
An equation describing the behavior of an electron in an atom.
Dipole-Dipole Force
An intermolecular force resulting from electrical interactions among dipoles on neighboring molecules.
Ion-Dipole Force
An intermolecular force resulting from electrical interactions between an ion and the partial charges on a polar molecule.
London Dispersion Force
An intermolecular force resulting from the presence of temporary dipoles in atoms or molecules.
Aufbau Principle
Applies to the formation of ionic compounds: Electrons given up by a metal in forming a cation come from the highest-energy occupied orbital, while the electrons that are accepted by a non-metal in forming an anion go into the lowest-energy occupied orbital.
Isoelectronic
Atoms or ions with the same electron configuration.
Construct correct Lewis dot structures for the three molecules below. SF4 PF 3 IF 3 I. II. III. 17. Determine which of these molecule(s) (see I-III above) exceed the octet rule. A. I and II B. I and III C. II and III D. only one of them E. all three of them
B
Determine the charge cloud geometry and the molecular shape of PF3. A. trigonal planar and trigonal planar B. tetrahedral and trigonal pyramidal C. trigonal planar and t-shaped D. trigonal bipyramidal and t-shaped E. tetrahedral and trigonal planar
B
Draw Lewis structures of the molecules below and use them to answer the following two questions I. AlH3 II. NÓ III. SeF6 IV. Ǒ V. XeF2 14. Which of these molecules (see I-V above) show resonance? A. I, IV B. II, IV C. II, V D. III, IV E. III, V
B
The bond length in the HI molecule is 161.0 pm and the measured dipole moment is 0.44 D (debyes). What is the percent ionic character in HI? (1 debye = 3.34 x 10^−30 coulomb-meters; electronic charge = e = 1.6 x 10^−19 coulombs). A. 2.7% B. 5.7% C. 18% D. 91% E. 94%
B
The orbital hybridization on the central carbon atom in allene, H2C=C=CH2, is A. unhybridized p B. sp C. sp2 D. sp3 E. sp4
B
Using a Born-Haber cycle, calculate the lattice energy for lithium fluoride, LiF(s), given the following data: Sublimation energy for Li(s) = 166 kJ ∕ mol first ionization energy for Li(g) = 520 kJ ∕ mol bond energy for F2(g) = 158 kJ ∕ mol electron affinity for F(g) = -328 kJ ∕ mol enthalpy of formation of LiF(s) = -617 kJ ∕ mol A. 1133 kJ ∕ mol B. 1054 kJ ∕ mol C. 329 kJ ∕ mol D. 180 kJ ∕ mol E. 101 kJ ∕ mol
B
What are the formal charges on the nitrogen atoms in NÓ− and NǑ− ? A. 0 and 0 B. 0 and +1 C. +1 and −1 D. +1 and +1 E. −1 and −1
B
Which of the following forms of V will have the most number of unpaired electrons? A. V B. V+ C. V2+ D. V3+ E. V4+
B
Which of the following has the bonds correctly arranged in order of increasing polarity? A. Be-F < Mg-F < N-F < O-F B. O-F < N-F < Be-F < Mg-F C. O-F < Be-F < Mg-F < N-F D. N-F < Be-F < Mg-F < O-F E. Mg-F < Be-F < N-F < O-F
B
Which of the following statements about resonance are true? I. Resonance hybrids occur because a compound changes back and forth between two or more resonance structures. II. Resonance structures differ in the arrangement of electrons but not in the arrangement of atoms. III. Resonance structures occur when there are two or more valid Lewis structures for a given compound. IV. Resonance structures for a given compound always contribute equally to the resonance hybrid A. I and II. B. II and III. C. II, III, and IV. D. I, III, and IV. E. I, II, and IV.
B
Which of these statements is false? A. Atomic radius increases on going down a group. B. Second ionization energies are always smaller than first ionization energies. C. A cation is always smaller than its parent neutral atom. D. Valence electrons are easier to remove than core electrons. E. Ionization energies increase on going from left to right across a period.
B
Draw Lewis structures of the molecules below and use them to answer the following two questions I. AlH3 II. NÓ III. SeF6 IV. Ǒ V. XeF2 How many of these molecules (see I-V above) have no net dipole moment? A. 1 B. 2 C. 3 D. 4 E. 5
C
H | H-C(triple bond)C-C-C-H 1 2 3 | H (4 is the other carbon) What are the molecular shapes around the atoms C3 and C4 (see figure above)? A. trigonal planar and trigonal pyramidal B. trigonal pyramidal and tetrahedral C. trigonal planar and tetrahedral D. trigonal pyramidal and trigonal planar E. tetrahedral and tetrahedral
C
The hybridization of nitrogen in NÓ− and NǑ− is: A. sp and sp B. sp2 and sp C. sp2 and sp2 D. sp3 and sp2 E. sp3 and sp3
C
What is the molecular shape of TeF4? A. square pyramidal B. trigonal bipyramidal C. seesaw D. octahedral E. tetrahedral
C
Chiral Center
The presence of a carbon atom with four different substituent groups.
Bonding Pair
The shared electrons.
Octet Rule
The statement that main-group elements tend to undergo reactions that leave them with eight valence electrons.
Lattice Energy (U)
The sum of the electrostatic interactions between ions in a solid that must be overcome to break a crystal into individual ions.
What is the geometry for atoms with 3 bonds, 0 lone pairs, and 3 charge clouds?
Trigonal Planar