Polar covalent bonds partial ionic character

Polar covalent bonds are covalent bonds with ionic character (partial election transfer). Ionic and covalent bonding are extremes forms of bonding polar bonds are intermediate in nature. The larger the difference in electronegativity between the atoms, the greater the polarity of the... 

When two atoms share electrons unequally, it means that the bond between them is polar. Another way to describe this is to say that the bond has partial ionic character. For the molecule AB, this is equivalent to drawing two structures, one of which is covalent and the other ionic. However, there are actually three structures that can be drawn... 

Eormula HE MW 20.006. A very stable polar covalent diatomic molecule H—E bond energy 136.1 kcaPmol at lower temperatures molecules are associated by hydrogen bonding H—bond length 0.92A partial ionic character 40% dipole moment 6.10 D hydrofluoric acid is an aqueous solution of hydrogen fluoride gas. 

Let us discuss the importance of charge separation in bonds involving atoms of different electronegativity, for example, C and N, O, or Cl. The extent of partial ionic character in such polar covalent bonds is a key factor in determining a compound s... 

However, many covalent bonds do not equally share electrons such covalent bonds, as pointed out above, are referred to as polar covalent bonds or bonds of partial ionic character. Electronegativity is rated on a relative scale ranging from 4 (most electronegative, fluorine) to 0.7 (least electronegative, cesium) (Table 1.7). In general, the greater the difference in electronegativity between two elements, the more ionic will be the bond between them (Fig. 1.2). 

When non-identical atoms are joined in a covalent bond, the electron pair will be attracted more strongly to the atom that has the higher electronegativity. As a consequence, the electrons will not be shared equally the center of the negative charges in the molecule will be displaced from the center of positive charge. Such bonds are said to be polar and to possess partial ionic character, and they may confer a polar nature on the molecule as a whole. 

Laboratory measurements show that most real bonds are neither fully ionic nor fully covalent, but instead possess a mixture of ionic and covalent character. Bonds in which there is a partial transfer of charge are called polar covalent. This section provides an approximate description of the polar covalent bond based on the relative abilities of each atom to attract the electron pair toward its nucleus. This ability is estimated by comparing the electronegativity values for the two atoms. 

Polar covalent bonds may be thought of as intermediate between pure (nonpolar) covalent bonds and pure ionic bonds. In fact, bond polarity is sometimes described in terms of partial ionic character. This usually increases with increasing difference in electronegativity between bonded atoms. Calculations based on the measured dipole moment of gaseous HCl indicate about 17% ionic character. ... 

When the electronegativity difference between bonding atoms is between 0.5 and 2.0, the electron sharing is not so rmequal that a complete transfer of electrons takes place. Instead, there is a partial transfer of the shared electrons to the more electronegative atom. The less electronegative atom stiU retains some attraction for the shared electrons. The bond that forms when electrons are shared unequally is called a polar covalent bond. A polar covalent bond has a significant degree of ionic character. 

The Partial Ionic Character of Polar Covalent Bonds... 

Although the designations covalent, polar covalent, and ionic can be useful, sometimes chemists wish to describe and compare chemical bonds with more precision. For this purpose, we can use Equation 8.1 to calculate the dipole moment we would expect if the chaiges on the atoms were discrete instead of partial that is, if an electron had actually been transferred from one atom to the other. Comparing this calculated dipole moment with the measured value gives us a quantitative way to describe the nature of a bond rising the term percent ionic character, which is defined as the ratio of observed p, to calculated p, multiplied by 100. 

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