A covalent bond in which the shared electron pair is unequally attracted by the two bonded atoms is called a polar bond.
Usually, a polar covalent bond exists between two unlike atoms. There are some molecules in which the shared electron pair is not equally attracted. For example ,when a covalent bond exists between two unlike atoms which are not identical, the electron pair between them will be attracted more towards one atom or the other, depending their electro negativity . The atom towards which the electron pair is attracted more will become slightly negatively charged while the other atom will become slightly positively charged. Such a covalent bond is called polar covalent bond.
Example
Consider the covalent bond in hydrogen chloride ,H-Cl . The chloride atom being more electronegative (EN. 3.0) than hydrogen atom (EN 2.1) attracts the shared electron pair more nearer to it and thus becomes a partially negatively charged and the hydrogen atom becomes partially positively charged. Thus giving partial ionic character to the covalent bond.
Thus the ionic character of covalent bond depends upon the difference of electro negativities of the two hydrogen atoms. The greater he electro negativity difference between the two bonded atoms , the greater is the polarity of the bond.
Usually, a polar covalent bond exists between two unlike atoms. There are some molecules in which the shared electron pair is not equally attracted. For example ,when a covalent bond exists between two unlike atoms which are not identical, the electron pair between them will be attracted more towards one atom or the other, depending their electro negativity . The atom towards which the electron pair is attracted more will become slightly negatively charged while the other atom will become slightly positively charged. Such a covalent bond is called polar covalent bond.
Example
Consider the covalent bond in hydrogen chloride ,H-Cl . The chloride atom being more electronegative (EN. 3.0) than hydrogen atom (EN 2.1) attracts the shared electron pair more nearer to it and thus becomes a partially negatively charged and the hydrogen atom becomes partially positively charged. Thus giving partial ionic character to the covalent bond.
Thus the ionic character of covalent bond depends upon the difference of electro negativities of the two hydrogen atoms. The greater he electro negativity difference between the two bonded atoms , the greater is the polarity of the bond.
