back

Chapter 11
Chemical Bonding I: Basic Concepts
 
 
 
Movie
Title
 Movie
Caption
 Demonstration of the reaction between sodium and chlorine to form sodium chloride
Notes
 Formation of Sodium Chloride. Molten sodium burns when it is put into a container of chlorine gas. In the reaction a sodium ion loses an electron to form a sodium cation and a chlorine atom simultaneously gains an electron to form a chloride anion. The product of the reaction is the ionic compound sodium chloride, which is the white solid observed.
Movie
Title
 Movie
Caption
 The change in potential energy as a function of H-H bond distance for H2 is illustrated in this animation.
Notes
 H2 Bond Formation. As two H atoms approach each other to form an H2 molecule their orbitals begin to overlap, resulting in a decrease in energy as the electron density between the nuclei increases. When the atoms are very close thenuclei repel each other, causing an increase in energy. The observed bond length is the distance at which the attractive and repulsive forces are balanced.
Movie
Title
 Movie
Caption
 Periodic Trends: Electronegativity
Notes
 Periodic trends: electronegativities. Electronegativity is the ability of an atom to attract the electrons in a bond to itself. Nonmetals have greater electronegativities than metals, consistent with the fact that they gain electrons in reactions with metals. Electronegativites increase from left to right across a period. A gradual but irregular increase in electronegativities is observed for the transition elements. Electronegativities decrease down a group.
Movie
Title
 Movie
Caption
 The calculation of formal charges and their use are demonstrated in this animation.
Notes
 Formal charge. Formal charges help predict the most stable isomer or the contribution of a resonance structure. The formal charge is the number of valence electrons associated with the free atom minus the number of electronsassociated with the atom in a molecule. In a molecule unshared electron pairs are assigned entirely to the atom they are associated with and shared electron pairs are assigned equally to the two atoms sharing them.
Movie
Title
 Movie
Caption
 Animation illustrating the periodic trend in oxidation states
Notes
 Periodic trends: Common Oxidation States. Elements in group IA and group IIA have oxidation numbers of +1 and +2, respectively. The maximum oxidation state increases from left to right across the periodic table. In the first row, O and F have negative oxidation numbers. In the second row S and Cl have positive oxidation numbers when they combine with O or F. In the third row the maximum oxidation number is +7 for Mn.
Movie
Title
 Movie
Caption
 Animation illustrating the periodic trends in atomic radii
Notes
 Periodic trends: Atomic radii. As we move down a group in the periodic table the effective nuclear charge is essentially unchanged while the principal quantum number increases, resulting in an increase in the atomic radius. From left to right across a period the shielding by the inner electrons remains nearly constant while the number of protons in the nucleus increases, causing the atomic radii to decrease.
Movie
Title
 Movie
Caption
 Repulsion between valence shell electron pairs
Notes
 VSEPR. The VSEPR model predicts electron-domain geometries, by assuming that electron domains assume positions as far apart as possible to minimize electron-electron repulsions. The electron-pair geometries associated with the number of electron domains are as follows: linear, 2 electron domains; trigonal planar, 3 electron domains, tetrahedral, 4 electron domains, trigonal-bipyramidal, 5 electron domains, and octahedral, 6 electron domains.
Movie
Title
 Movie
Caption
 Demonstration of the synthesis of nylon 610
Notes
 Synthesis of Nylon 610. Nylon 610 is a condensation polymer formed by the reaction of decanedioyl dichloride and 1,6-diaminohexane. The 1,6-diaminohexane is dissolved in a solution of NaOH and poured into a beaker containing decanedioyl dichloride. The reaction takes place at the interface between the two liquids. The nylon forms a string which can be pulled out of the solution. The reaction continues at the interface as the nylon is removed.
11.0.1UN
Title
 Lewis p 389
Caption
 Gilbert Newton Lewis (1875-1946). Lewis’s contribution to the study of chemical bonding is evident throughout this text. Equally important, however, was his pioneering introduction of thermodynamics into chemistry
Notes
  
11.1
Title
 11-1
Caption
 Portion of an ionic crystal. This structure of alternating Na1 and Cl2 ions extends in all directions and involves countless numbers of ions.
Notes
  
11.3
Title
 11-3
Caption
 Paramagnetism of oxygen (also Fig. 12.24.04.UN)
Notes
  
11.4
Title
 11-4
Caption
 Nonpolar and polar covalent bonds. (a) In the diatomic nonpolar molecules H2 and Cl2, the center of positive charge lies midway between the atomic nuclei along a line between them. The center of negative charge comes at the same point. There is no charge separation. (b) In the HOCl bond the center of positive charge lies much closer to the Cl nucleus than to the H nucleus, but this is because the Cl nucleus has 17 units of positive charge compared with just 1 unit for H. The center of negative charge lies still closer to the Cl nucleus. This is because of the stronger attraction of Cl than of H for the electron pair in the HOCl bond. In a polar covalent bond the centers of positive and negative charge are separated.
Notes
  
11.5
Title
 11-5
Caption
 An analogy to a polar covalent bond. The geographical center of the contiguous 48 states of the United States remains fixed (Æ), but the population center (O) is moving to the south and west. The separation between these two centers is analogous to the separation of the centers of positive and negative charge in a polar covalent bond. As the distance between the centers becomes smaller, the bond becomes less polar.
Notes
  
11.6
Title
 11-6
Caption
 Electronegativities of the elements. As a general rule, electronegativities decrease from top to bottom in a group and increase from left to right in a period of elements. The values are from L. Pauling, The Nature of the Chemical Bond, 3rd edition, Cornell University, Ithaca, NY, 1960, p. 93. They may be somewhat different from values based on other scales
Notes
  
11.7
Title
 11-7
Caption
 Percent ionic character of a chemical bond as a function of electronegativity difference
Notes
  
11.8
Title
 11-8
Caption
  
Notes
 Summary scheme for drawing Lewis structures
11.9
Title
 11-9
Caption
  
Notes
 Geometric shape of a molecule
11.10
Title
 11-10
Caption
 Balloon analogy to valence-shell electron-pair repulsion. When two elongated balloons are twisted together, they separate into four lobes. To minimize interferences, the lobes spread out into a tetrahedral pattern. (A regular tetrahedron has four faces, each an equilateral triangle.) The lobes are analogous to valence-shell electron pairs.
Notes
  
11.11a,b,c-BC
Title
 11-11
Caption
 Molecular shapes based on tetrahedral electron group geometry-CH4, NH3, and H2O. Molecular shapes are established by the blue lines. Lone pair electrons are shown as red dots along broken lines originating at the central atom. (a) All electron groups around the central atom are bond pairs. The blue lines that outline the molecule are different from the black lines representing the carbon-to-hydrogen bonds. (b) The lone pair of electrons is directed to the “missing” corner of the tetrahedron. The nitrogen-to-hydrogen bonds form three of the edges of a trigonal pyramid. (c) The H2O molecule is a bent molecule outlined by the two oxygen-to-hydrogen bonds
Notes
  
11.12
Title
 11-12
Caption
  
Notes
 Several electron-group geometries illustrated
11.12.6T1
Title
 12-4
Caption
 CH4
Notes
  
11.13
Title
 11-13
Caption
 Two predictions of the structure of ICl42-Example 11-9 illustrated. The observed structure is the square planar structure.
Notes
  
11.14
Title
 11-14
Caption
  
Notes
 Polar molecules in an electric field
11.15
Title
 11-15
Caption
 Molecular shapes and dipole moments. (a) The resultant of two of the COCl bond moments is shown as a red arrow, and that of the other two, as a blue arrow. The red and blue arrows point in opposite directions and cancel. The CCl4 molecule is nonpolar. (b) The individual bond moments do combine to yield a resultant dipole moment (red arrow) of 1.01 D
Notes
  
11.16
Title
 11-16
Caption
 Some bond energies compared. The same quantity of energy, 435.93 kJ/mol, is required to break all HOH bonds. In H2O, more energy is required to break the first bond (498.7 kJ/mol) than to break the second (428.0 kJ/mol). The second bond broken is that in the OH radical. The OOH bond energy in H2O is the average of the two values: 463.4 kJ/mol.
Notes
  
11.17
Title
 11-17
Caption
 Net bond breakage and formation in a chemical reaction-Example 11-13 illustrated. Bonds that are broken are shown in red, and bonds that are formed, in blue. Bonds that remain unchanged are in black. The net change is that one COH and one ClOCl bond break and one COCl and one HOCl bond form.
Notes
  
P 426
Title
 P 426
Caption
  
Notes
 In 1934, Wallace CarothersÉ.
Table 11.1a
Title
 Table 11.1
Caption
  
Notes
 Molecular Geometry as a Function of Electron Group Geometry
Table 11.2
Title
 Table 11.2
Caption
  
Notes
 Some Average Bond Lengths
Table 11.3
Title
 Table 11.3
Caption
  
Notes
 Some Average Bond Energies
Table 11.1b
Title
 Table 11.1
Caption
  
Notes
 Molecular Geometry as a Function of Electron Group Geometry