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Key Concepts PowerPoint

Chapter 7
Covalent Bonds and Molecular Structure

 
07-01
Title
The Covalent Bond
Caption
Figure 7.1 A covalent H-H bond is the net result of attractive and repulsive electrostatic forces. The nucleus-electron attractions (blue arrows) are greater than the nucleus-nucleus and electron-electron repulsions (red arrows), resulting in a net attractive force that holds the atoms together to form an H2 molecule.
Notes
The covalent bond between two hydrogen atoms
Keywords
covalent bonding
07-02
Title
Bond Length
Caption
Figure 7.2 A graph of potential energy versus internuclear distance for the H2 molecule. If the hydrogen atoms are too far apart, attractions are weak and no bonding occurs. If the atoms are too close, strong repulsions occur. When the atoms are optimally separated, the energy is at a minimum.
Notes
Bond length defined as the internuclear distance when energy is at a minimum
Keywords
bond length
07-02-01UN
Title
Bond Energy
Caption
Bond dissociation energy (D) is the amount of energy required to break a bond in a molecule in the gaseous state. Consequently, D values are always positive, while the formation of the bond would have the same magnitude but opposite sign.
Notes
Bond dissociation energy same magnitude as energy released by bond formation
Keywords
bond energy, bond dissociation energy
07-03
Title
Polar Covalent Bonds
Caption
Figure 7.3 The bonding continuum from ionic to nonpolar covalent. Polar covalent bonds lie between the two extremes. They are characterized by an unsymmetrical electron distribution in which the bonding electrons are attracted somewhat more strongly by one atom than the other. The symbol d (Greek delta) means partial charge, either partial positive (d+) or partial negative (d-).
Notes
Electronegativity differences between two atoms results in a polar covalent bond
Keywords
polar covalent, electronegativity
07-03-01UN
Title
Sodium chloride: Ionic bond
Caption
Large differences in electronegativity yield compounds whose bonds can be referred to as ionic.
Notes
Ionic bonding in NaCl
Keywords
ionic bond
07-03-02UN
Title
Polar Covalent Bond
Caption
Chlorine is more electronegative than hydrogen, resulting in a bond from unequal sharing of electrons between the two atoms called a polar covalent bond.
Notes
Polar covalent bond in hydrogen chloride, HCl
Keywords
polar covalent
07-03-03UN
Title
Nonpolar Covalent Bond
Caption
When the electronegativity difference between the two atoms is very small or zero, the resulting bond is called a nonpolar covalent bond, since the bonding electrons are essentially equally shared.
Notes
Nonpolar covalent bond in chlorine, Cl2
Keywords
nonpolar covalent
07-04
Title
Electronegativity Trends
Caption
Figure 7.4 Electronegativity trends in the periodic table. Electronegativity increases from left to right and generally decreases from top to bottom.
Notes
Electronegativity trends in the periodic table
Keywords
electronegativity
07-04-04UN
Title
Electron-Dot Structures
Caption
The electron-dot structure of the hydrogen molecule represents the sharing of an electron from each hydrogen atom to form a bonding pair of electrons.
Notes
Electron-dot structures and bonding pairs of electrons
Keywords
electron-dot, bonding
07-04-13UN
Title
Multiple Bonds and Bond Lengths
Caption
As the bond order increases between two atoms, the observed distance between them decreases as shown in the figure for O-O and N-N bonds.
Notes
Bond length is inversely proportional to bond order between two atoms
Keywords
multiple bonds, bond lengths, bond order
07-04-15UN
Title
Structures of Polyatomic Molecules
Caption
Naturally occurring molecules generally consist of compounds that have bonds involving hydrogen and the three second-row elements shown in the diagram: carbon, nitrogen, and oxygen.
Notes
Electron-dot structures of polyatomic molecules
Keywords
polyatomic molecules, electron-dot
07-04-16
Title
Electron-Dot Structures of Molecules
Caption
Electron-dot structures usually use a line to represent a bonding pair of electrons.
Notes
Electron-dot structures of polyatomic molecules
Keywords
electron-dot structures
07-04-17UN
Title
Worked Example 7.2
Caption
While a line is used to represent a bonding pair of electrons, dots are still used to represent nonbonding electrons.
Notes
Electron-dot structure of hydrazine, N2H4
Keywords
hydrazine, electron-dot
07-04-18UN
Title
Structure of carbon dioxide
Caption
Electron-dot structure and space-filling model of carbon dioxide.
Notes
For Worked Example 7.3
Keywords
carbon dioxide, structure
07-04-19UN
Title
Structure of hydrogen cyanide
Caption
Electron-dot structure and space-filling model of hydrogen cyanide, HCN.
Notes
For Worked Example 7.4
Keywords
hydrogen cyanide, structure
07-04-20UN
Title
Incomplete Structure of Histidine
Caption
Ball-and-stick model of histidine.
Notes
For Key Concept Example 7.5
Keywords
histidine
07-04-21UN
Title
Bonding Within Histidine
Caption
Arrows indicate where bonds and nonbonding electrons are needed to complete the structure.
Notes
Working structure for Key Concept Problem 7.5
Keywords
histidine
07-04-22UN
Title
Finished Structure of Histidine
Caption
All bonding and nonbonding electrons are now shown in the structure of histidine.
Notes
Completed structure of histidine for Key Concept Example 7.5
Keywords
histidine
07-04-23UN
Title
Key Concept Problem 7.8
Caption
Ball-and-stick structure of cytosine.
Notes
Key concept problem 7.8
Keywords
cytosine
07-04-24UN
Title
Compounds with Elements Below the Second Row
Caption
Periodic table highlighting the elements that form compounds which tend to access low-energy d orbitals and effectively 'expanding the octet.'
Notes
Formation of compounds that "violate" the octet rule
Keywords
octet rule, expanded octet
07-04-29UN
Title
Structure of sulfur tetrafluoride, SF4
Caption
Electron-dot structure and space-filling model for sulfur tetrafluoride.
Notes
Electron-dot structure of SF4
Keywords
electron-dot structure, expanded octet
07-04-31UN
Title
Structure of phosphorus pentachloride, PCl5
Caption
Space-filling model showing the geometry of the PCl5 molecule.
Notes
Structure of PCl5 for Worked Example 7.6
Keywords
phosphorus pentachloride
07-04-37UN
Title
Structure of xenon pentafluoride cation
Caption
Electron-dot structure and space-filling model of xenon pentafluoride ion.
Notes
For Worked Example 7.8
Keywords
xenon pentafluoride
07-04-40UN
Title
Resonance Structures
Caption
Two equivalent resonance structures and a space-filling model of ozone, O3.
Notes
Structures of ozone
Keywords
ozone, resonance
07-04-44UN
Title
Key Concept Problem 7.14
Caption
Ball-and-stick structure of anisole.
Notes
Key concept problem 7.14
Keywords
key concept, resonance
07-04-48UN
Title
Acetamide
Caption
Space-filling model of acetamide, C2H5NO.
Notes
Structure of acetamide
Keywords
acetamide
07-04-50UN
Title
Nitrous oxide
Caption
Space-filling model of nitrous oxide, N2O.
Notes
Structure of nitrous oxide
Keywords
nitrous oxide
07-04-54UN
Title
Molecular shapes
Caption
Three-dimensional structures of water, ammonia, and methane.
Notes
In the annotated structures, a line represents a bond that lies in the plane, a dashed line (or dashed wedge) represents a bond that is pointed away from the viewer, and a solid wedge represents a bond that is pointed towards the viewer.
Keywords
VSEPR, molecular shapes
07-04-55UN
Title
Two Charge Clouds
Caption
Structures of carbon dioxide and hydrogen cyanide showing the linear geometry.
Notes
Two charge clouds results in linear electronic geometry
Keywords
charge clouds, linear, VSEPR
07-04-56UN
Title
Three Charge Clouds
Caption
Structures of formaldehyde and sulfur dioxide showing the trigonal planar geometry.
Notes
Three charge clouds results in a trigonal planar electronic geometry
Keywords
charge clouds, trigonal planar, VSEPR
07-05a-c
Title
Four Charge Clouds
Caption
Figure 7.5 The tetrahedral geometry of an atom surrounded by four charge clouds. The atom is located in the center of a regular tetrahedron (a), and the four charge clouds point toward the four corners (b). The angle between any two bonds is exactly 109.5° (c).
Notes
Four charge clouds result in a tetrahedral electronic geometry
Keywords
charge clouds, tetrahedral, VSEPR
07-05-01UN
Title
Four Charge Clouds
Caption
Structures of methane, ammonia, and water showing the tetrahedral electronic geometry.
Notes
Although four charge clouds results in a tetrahedral electronic geometry, the molecular geometry is subsequently determined by looking only at the bonding pairs of electrons.
Keywords
charge clouds, tetrahedral, VSEPR
07-05-02UN
Title
Five Charge Clouds
Caption
Trigonal pyramid geometry of an atom surrounded by five charge clouds.
Notes
Five charge clouds results in a trigonal bypyramid electronic geometry
Keywords
charge clouds, trigonal bipyramid, VSEPR
07-05-03UN
Title
Phosphorus pentachloride
Caption
Trigonal bipyramid structure of phosphorus pentachloride, PCl5.
Notes
Structure of phosphorus pentachloride
Keywords
phosphorus pentachloride, trigonal bipyramid
07-05-04UN
Title
Sulfur tetrafluoride
Caption
Trigonal bipyramid electronic structure of sulfur tetrafluoride results in a seesaw molecular shape.
Notes
Structure of sulfur tetrafluoride, SF4
Keywords
sulfur tetrafluoride, trigonal bipyramid, seesaw
07-05-05UN
Title
Chlorine trifluoride
Caption
Structure of chlorine trifluoride showing the trigonal bipyramid electronic geometry and the molecular T-shape.
Notes
Structure of chlorine trifluoride, ClF3
Keywords
chlorine trifluoride, trigonal bipyramid, T-shape
07-05-06UN
Title
Triiodide ion
Caption
Structure of the triiodide ion showing the trigonal bipyramid electronic geometry and the linear molecular shape.
Notes
Structure of triiodide ion
Keywords
triiodide, trigonal bipyramid, linear
07-05-07UN
Title
Six Charge Clouds
Caption
Regular octahedral geometry of an atom surrounded by six charge clouds.
Notes
Six charge clouds results in an octahedral electronic geometry
Keywords
charge clouds, octahedral, VSEPR
07-05-08UN
Title
Sulfur hexafluoride
Caption
Structure of sulfur hexafluoride showing the octahedral electronic and molecular geometry.
Notes
Structure of sulfur hexafluoride, SF6
Keywords
sulfur hexafluoride, octahedral
07-05-09UN
Title
Antimony pentachloride ion
Caption
Structure of the antimony pentachloride ion showing the octahedral electronic geometry and the square pyramidal molecular shape.
Notes
Structure of antimony pentachloride ion, SbCl52-
Keywords
antimony pentachloride, octahedral, square pyramid
07-05-10UN
Title
Xenon tetrafluoride
Caption
Structure of xenon tetrafluoride showing the octahedral electronic geometry and the square planar molecular shape.
Notes
Structure of xenon tetrafluoride, XeF4
Keywords
xenon tetrafluoride, octahedral, square planar
07-05-11UN
Title
Table 7.4 Molecular Geometry (part 1)
Caption
Notes
Electronic and molecular geometries
Keywords
table, geometries, charge clouds
07-05-12UN
Title
Table 7.4 Molecular Geometry (part 2)
Caption
Notes
Electronic and molecular geometries
Keywords
table, geometries, charge clouds
07-05-13UN
Title
Structure of Ethylene
Caption
Structure of ethylene showing the trigonal planar geometry around each carbon atom.
Notes
Structure of ethylene
Keywords
ethylene, trigonal planar
07-05-16UN
Title
Bromine pentafluoride
Caption
Structure of bromine pentafluoride showing the octahedral electronic geometry and square pyramid molecular shape.
Notes
Structure of bromine pentafluoride, BrF5, for Example 7.11
Keywords
bromine pentafluoride, octahedral, square pyramid
07-05-17UN
Title
Key Concept Problem 7.19
Caption
What is the geometry around the central atom in each of the following molecular models?
Notes
Key concept problem 7.19
Keywords
key concept, geometry
07-05-18UN
Title
Valence bond theory—H2
Caption
Overlap of two singly occupied 1s orbitals to form the hydrogen molecule according to valence bond theory.
Notes
Valence bond theory
Keywords
valence bond theory
07-05-19UN
Title
Valence bond theory—F2
Caption
Valence bond theory proposes that the sigma bond between the two fluorine atoms results from overlap of the two singly occupied 2p orbitals.
Notes
Valence bond theory suggests that orbital overlap has directionality associated with it.
Keywords
valence bond theory
07-05-20UN
Title
Valence bond theory—HCl
Caption
Valence bond theory suggests that the sigma bond in HCl results from the overlap of the 1s orbital of hydrogen and the 3p orbital of chlorine.
Notes
Valence bond theory
Keywords
valence bond theory
07-05-21UN
Title
Tetravalent Carbon
Caption
In order for carbon to form four bonds, valence bond theory would suggest that an electron from the filled 2s orbital would have to be excited to the empty 2p orbital, giving the excited-state electron configuration shown. However, this configuration does not account for the four bonds of carbon actually being equivalent and the tetrahedral geometry of carbon molecules like methane.
Notes
Limitations of the valence bond theory
Keywords
valence bond theory, hybridization
07-05-22UN
Title
Orbital Hybridization
Caption
In 1931, Linus Pauling proposed that the wave functions for the s and p atomic orbitals can be mathematically combined to form a new set of equivalent wave functions called hybrid orbitals.
Notes
Mixing one s orbital with three p orbitals yields four equivalent sp3 hybrid orbitals.
Keywords
hybridization, hybrid orbitals
07-06
Title
Hybrid Orbitals
Caption
Figure 7.6 The formation of four sp3 hybrid orbitals by combination of an atomic s orbital with three atomic p orbitals. Each sp3 hybrid orbital has two lobes, one of which is larger than the other. The four large lobes are oriented toward the corners of a tetrahedron at angles of 109.5°.
Notes
Mixing one s orbital with three p orbitals yields four equivalent sp3 hybrid orbitals.
Keywords
hybridization, hybrid orbitals
07-07
Title
Orbital Picture of Methane
Caption
Figure 7.7 The bonding in methane. Each of the four C-H bonds results from head-on (s) overlap of a singly occupied carbon sp3 hybrid orbital with a singly occupied hydrogen 1s orbital.
Notes
Sigma bonds are formed by head-to-head overlap between the hydrogen s orbital and a singly occupied sp3 hybrid orbital of carbon.
Keywords
hybrid orbitals, hybridization, sp3
07-07-01UN
Title
Hybridization and VSEPR Theory
Caption
The same concept of orbital hybridization can be used to describe the electronic geometry and molecular shape of other molecules predicted by VSEPR theory.
Notes
Hybridization and VSEPR theory describing molecular shape
Keywords
hybridization, VSEPR, geometry, molecular shape
07-08
Title
Other Hybrid Orbitals: sp2
Caption
Figure 7.8 The formation of sp2 hybrid orbitals by combination of one s orbital and two p orbitals. The three hybrids lie in a plane at angles of 120° to one another. One unhybridized p orbital remains, oriented at a 90° angle to the plane of the sp2 orbitals.
Notes
sp2 hybridization accounts for trigonal planar geometries
Keywords
hybridization, sp2
07-08-01UN
Title
Modes of Bonding
Caption
Hybrid orbitals are limited to sigma (head-to-head) overlap, whereas unhybridized p orbitals can engage in parallel overlap called pi bonding.
Notes
Sigma and pi bonding
Keywords
hybridization, pi, sigma, bonding
07-09
Title
Bonding in Ethylene
Caption
Figure 7.9 The structure of ethylene. The carbon-carbon double bond consists of one s bond from the head-on overlap of sp2 orbitals and one p bond from the sideways overlap of p orbitals. The four C-H s bonds result from overlap of carbon sp2 orbitals with hydrogen 1s orbitals. The overall shape of the molecule is planar (flat), with H-C-H and H-C-C bond angles of approximately 120°.
Notes
Sigma and pi bonding in ethylene
Keywords
ethylene, sigma, pi, multiple bonds
07-10
Title
Other Hybrid Orbitals: sp
Caption
Figure 7.10 The combination of one s and one p orbital gives two sp hybrid orbitals oriented 180° apart. Two unhybridized p orbitals remain and are oriented at 90° angles to the sp hybrids.
Notes
sp hybridization accounts for linear geometries
Keywords
hybridization, sp
07-11
Title
Bonding in Acetylene
Caption
Figure 7.11 Formation of a triple bond by two sp-hybridized atoms. A s bond forms by head-on overlap of sp orbitals, and two mutually perpendicular p bonds form by sideways overlap of p orbitals.
Notes
Sigma and pi bonding in acetylene
Keywords
acetylene, sigma, pi, bonding
07-12
Title
Other Hybrid Orbitals: sp3d
Caption
Figure 7.12 The five sp3d hybrid orbitals and their trigonal bipyramidal geometry.
Notes
Although at first glance the sp3d hybrid structure looks similar to sp2 hybrization, note that in the sp3d structure all five orbitals are hybrids and can only engage in sigma bonding, yielding the trigonal bipyramid geometry.
Keywords
hybridization, sp3d
07-13
Title
Other Hybrid Orbitals: sp
Caption
Figure 7.13 The six sp3d2 hybrid orbitals and their octahedral geometry.
Notes
Although at first glance the sp3d2 hybrid structure looks similar to sp hybridization, note that in the sp3d2 structure all six orbitals are hybrids and can only engage in sigma bonding, yielding the octahedral geometry.
Keywords
hybridization, sp3d2
07-13-02UN
Title
Orbital structure of allene
Caption
Due to the observed geometry of the molecule, the central carbon must be sp hybridized and the other two carbons are sp2 hybridized.
Notes
Structure and geometry of allene for Example 7.12
Keywords
allene, hybridization, geometry
07-13-03UN
Title
Key Concept Problem 7.25
Caption
Identify each of the following sets of hybrid orbitals.
Notes
Key concept problem 7.25
Keywords
key concept, hybridization
07-14
Title
Formation of molecular orbitals
Caption
The wave functions of two atomic orbitals can be combined in a subtractive manner producing an antibonding molecular orbital, or in an additive manner producing a bonding molecular orbital.
Notes
Bonding and antibonding molecular orbitals
Keywords
atomic orbital, molecular orbital, bonding, antibonding
07-15
Title
Molecular Orbital Diagram
Caption
Figure 7.15 A molecular orbital diagram for the H2 molecule. The two electrons are paired in the bonding s MO, and the antibonding s* MO is vacant.
Notes
Bonding and antibonding molecular orbitals
Keywords
atomic orbital, molecular orbital, bonding, antibonding
07-16
Title
MO Diagrams for H2-ion and He2 molecule
Caption
Figure 7.16 MO diagrams for (a) the stable H2-ion and (b) the unstable He2 molecule.
Notes
MO theory predicting molecular stability
Keywords
molecular orbitals, antibonding, bonding
07-18
Title
MO Diagrams for Diatomic Molecules
Caption
Figure 7.18 Molecular orbital energy diagrams for (a) N2 and (b) O2 and F2. There are eight MOs, four bonding and four antibonding. The two diagrams differ only in the relative energies of the s2p and p2p orbitals.
Notes
MO theory explains the paramagnetic property of molecular oxygen
Keywords
MO theory, diamagnetic, paramagnetic
07-19
Title
Formation of Molecular Orbitals from p atomic orbitals
Caption
Atomic p orbitals can be combined head-to-head yielding sigma bonding and sigma antibonding molecular orbitals, and can be combined parallel yielding pi bonding and pi antibonding molecular orbitals.
Notes
Formation of sigma and pi, bonding and antibonding, molecular orbitals.
Keywords
molecular orbitals, sigma, pi, bonding, antibonding
07-20
Title
MO Diagrams for Some Diatomic Molecules
Caption
Figure 7.20 Molecular orbital diagrams for the second-row diatomic molecules (a) N2, (b) O2, and (c) F2. The O2 molecule has two unpaired electrons in its two degenerate p*2p orbitals and is therefore paramagnetic.
Notes
Unpaired electrons in degenerate orbitals of oxygen explains the molecule's observed paramagnetism
Keywords
MO diagrams, paramagnetic, diamagnetic
07-21
Title
Orbital Picture of Ozone
Caption
Figure 7.21 The ozone molecule is a hybrid of two resonance forms that differ only in the location of p electrons. The nuclei and the s-bond electrons are in the same position in both resonance structures.
Notes
The strengths of valence bond theory and molecular orbital theory explain the bonding and electron delocalization observed in the resonance structures of ozone.
Keywords
ozone, resonance, delocalization
07-21-01
Title
Resonance hybrid structure of ozone
Caption
Resonance hybrid structure of ozone showing the delocalization of the pi electrons.
Notes
Resonance hybrid structure of ozone
Keywords
resonance hybrid, ozone
07-21-03UN
Title
Importance of Molecular Shape
Caption
Three-dimensional structure of a molecule can have a profound effect on its reactivity and biological activity. Although Levomethorphan and Dextromethorphan appear identical, they are actually mirror images of each other with very different biological activities.
Notes
Just like your left hand and right hand are not identical but mirror images of each other, so it is with some pairs of molecules. Consequently, such molecules are described as having "handedness."
Keywords
handedness, molecular shape, reactivity
07-21-04UN
Title
Handedness in Carvone
Caption
Two plants both produce carvone, but the mint leaves yield the “left-handed” form, while the caraway seeds yield the “right-handed” form.
Notes
l-carvone (odor of spearmint), d-carvone (odor of caraway)
Keywords
carvone, spearmint, caraway
07-21-05UN
Title
Key Concept Problem 7.30
Caption
One of the following two molecules has handedness to it and can exist in two mirror-image forms; the other does not. Which is which? Why?
Notes
Key concept problem 7.30
Keywords
key concept, handedness
07-21-050UN
Title
Key Concept Summary
Caption
Covalent bonds and molecular structure key concept summary.
Notes
Key concept summary Chapter 7
Keywords
key concept,