224
8 Models of Chemical Bonding and “Empirical” Methods
Fig. 8.5 Dependence of the C–C single bond length (in pm) on the number of adjacent bonds or
atoms
whereas the linear approximation gives
r e (n) = 130.6(10) + 3.70(23)n
(8.19)
with a standard deviation of 0.7 pm.
Similar equations as (8.17) seem to be also valid for compounds containing the
C=O and C≡N groups.
8.6 Appendix: Electronegativity (χ)
8.6.1 Introduction
Electronegativity is a measure of the relative ability of an atom in a molecule to
attract electrons to itself. It is generally a dimensionless parameter. It is an essential property of the atoms in a molecule, and several correlations have been shown
between electronegativity and molecular properties; see Sect. 8.5.3.1. In particular,
electronegativity helps characterize the bonding between the atoms, e.g., the bond
polarity. The difficulty is that electronegativity is defined artificially using an arbitrary
scale, and there are several different definitions.
8.6.2 Pauling Scale (Pauling 1932, 1960)
Pauling assumed that if two diatomic homonuclear molecules AA and BB interact
to form diatomic heteronuclear molecules AB, the bond energy of AB should be
the average of the two homonuclear bond energies of AA and BB, provided that
the electrons are shared evenly. However, the observed heteronuclear bond energy is
8 Models of Chemical Bonding and “Empirical” Methods
Fig. 8.5 Dependence of the C–C single bond length (in pm) on the number of adjacent bonds or
atoms
whereas the linear approximation gives
r e (n) = 130.6(10) + 3.70(23)n
(8.19)
with a standard deviation of 0.7 pm.
Similar equations as (8.17) seem to be also valid for compounds containing the
C=O and C≡N groups.
8.6 Appendix: Electronegativity (χ)
8.6.1 Introduction
Electronegativity is a measure of the relative ability of an atom in a molecule to
attract electrons to itself. It is generally a dimensionless parameter. It is an essential property of the atoms in a molecule, and several correlations have been shown
between electronegativity and molecular properties; see Sect. 8.5.3.1. In particular,
electronegativity helps characterize the bonding between the atoms, e.g., the bond
polarity. The difficulty is that electronegativity is defined artificially using an arbitrary
scale, and there are several different definitions.
8.6.2 Pauling Scale (Pauling 1932, 1960)
Pauling assumed that if two diatomic homonuclear molecules AA and BB interact
to form diatomic heteronuclear molecules AB, the bond energy of AB should be
the average of the two homonuclear bond energies of AA and BB, provided that
the electrons are shared evenly. However, the observed heteronuclear bond energy is