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WHAT ARE Polar Covalent Bonds PLEASE DESCRIBE WITH SOME EXAMPLES TO UNDERSTAND FOR ME

WHAT ARE Polar Covalent Bonds  PLEASE DESCRIBE   WITH SOME EXAMPLES TO UNDERSTAND FOR ME 

Grade:12

2 Answers

Gayatri Jayesh Bondriya
521 Points
6 years ago
Polar Covalent Bonds
In our discussion of chemical bonds in Section 1.4, we examined compounds such as LiF
in which the bond is between two atoms with very large electronegativity differences. In
instances like these, we said, a complete transfer of electrons occurs, giving the compound
an ionic bond:
 
 
We also described molecules in which electronegativity differences are not large, or in which
they are the same, such as the carbon–carbon bond of ethane. Here the electrons are shared
equally between the atoms.
 
 
Until now, we have not considered the possibility that the electrons of a covalent bond might
be shared unequally
 
 
 
 If electronegativity differences exist between two bonded atoms, and they are not
large, the electrons are not shared equally and a polar covalent bond is the result.
 Remember: One definition of electronegativity is the ability of an atom to attract
electrons that it is sharing in a covalent bond.
An example of such a polar covalent bond is the one in hydrogen chloride. The chlorine
atom, with its greater electronegativity, pulls the bonding electrons closer to it. This makes
the hydrogen atom somewhat electron deficient and gives it a partial positive charge (d).
The chlorine atom becomes somewhat electron rich and bears a partial negative charge (d):
 
 
 
 
 
 
Because the hydrogen chloride molecule has a partially positive end and a partially negative
end, it is a dipole, and it has a dipole moment.
The direction of polarity of a polar bond can be symbolized by a vector quantity
The crossed end of the arrow is the positive end and the arrowhead is the negative end:
 
 
 
The charges are typically on the order of 1010 esu and the distances are on the order
of 108 cm. Dipole moments, therefore, are typically on the order of 1018 esu·cm. For
convenience, this unit, 1  1018 esu cm, is defined as one debye and is abbreviated D.
(The unit is named after Peter J. W. Debye, a chemist born in the Netherlands, who taught
at Cornell University from 1936 to 1966. Debye won the Nobel Prize in Chemistry in 1936.)
In SI units 1 D  3.336  1030 coulomb meter (C · m).
If necessary, the length of the arrow can be used to indicate the magnitude of the dipole
moment. Dipole moments, as we shall see in Section 2.3, are very useful quantities in
accounting for physical properties of compounds.
 
 
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Gayatri Jayesh Bondriya
521 Points
6 years ago
Polar covalent bonds strongly influence the physical properties and reactivity of molecules.
In many cases, these polar covalent bonds are part of functional groups, which we
shall study shortly (Sections 2.5–2.13). Functional groups are defined groups of atoms in
a molecule that give rise to the function (reactivity or physical properties) of the molecule.
Functional groups often contain atoms having different electronegativity values and
unshared electron pairs. (Atoms such as oxygen, nitrogen, and sulfur that form covalent
bonds and have unshared electron pairs are called heteroatoms.)

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