Nature of C-X bond

The C–X bond in haloarene is polarized  as halogens are more electronegative than carbon.As we know  due to high electronegativity of halogen it attracts the electron cloud more towards itself and thus gains its negative charge similarly on the other hand carbon obtains a slight positive charge.
As halogens need only one electron to achieve their nearest stable  gas configuration  only one single bond is formed between one carbon and one halogen atom. 
Due to the increase in atomic size from fluorine to astatine   the C-X bond length in haloarene increases from fluorine to astatine and  the bond dissociation strength decreases   so dipole moment depends on the difference in electronegativity of carbon and halogens and as we all  know that the electronegativity of halogens decreases down the group  the dipole moment also decreases. As we know there is an exception of C–Cl and C–F dipole moments. Though the electronegativity of Chlorine is less than Fluorine, the dipole moment of C–Cl bond is more than C–F.

Chemical compounds containing arenes are known as haloarenes, where one  hydrogen atom bonded to an aromatic ring is replaced with halogens. It contains halogen atoms attached to sp2 hybridized carbon atoms of an aryl group. The C-–X bond nature depends on both the halogen of the compound and the nature of carbon. The X generally denotes halogen. Halogens are group seventeen elements that have very high electronegative. As we know going down the group  the elements are namely  (F),  (Cl),  (Br),  (I), and  (At). The highest electronegativity is fluorine . These  elements need  one more electron to complete the nearest stable gas configuration. In haloarenes, carbon of benzene is bonded to halogen. Electronegativity of halogen is more than that of sp2 hybridized carbon of the benzene ring. So,the C- X bond is a polar bond. Apart from this, lone pairs of electronS of halogen atoms are involved in resonance with the benzene ring. So, this C- X bond has acquired partial bond character.
This C-X bond of haloarenes is less polar than the C-X bond of haloalkanes. This is supported by the fact that the dipole moment of chlorobenzene is little lower than that of CH3CI. X is more electronegative than carbon. So, the C-X bond is polarized with C having a partial positive charge and X having a partial negative charge.

Important  Points on the Nature of C-X Bond in Haloarenes are as follows

These are the following points on the nature of C–X bonds in haloarenes are as follows: 

(1)As we know that the halogens are more electronegative than carbon and due to this high electronegativity  it makes the electron cloud attract more towards itself and therefore gains a little  negative charge  while the carbon attains a slight positive charge.  The C-X bond in haloarenes is polarized.

(2)Between one carbon atom and one halogen atom  only one sigma bond is formed because halogens need only one electron to reach the nearest stable gas configuration  that is the octet state.

(3)The atomic size increases from F to Ast   therefore, as a result, the C–X bond length in haloarenes also increases, and the bond dissociation strength decreases.

(4)Going  down the group the electronegativity power  decreases and we know that the dipole moment depends on the difference in electronegativity of carbon and halogens. Therefore, the dipole moment also decreases  as we go down the group. Although there is an exception of C–-Cl and C–-F dipole moments Cl has less electronegativity than F, but the dipole moment of C–-Cl bond is more than C-–F. 

Conclusion

 As we can conclude that the C-X bond is highly polar in nature because halogen atoms are electronegative and the carbon atom is electropositive. The electronegativity of the halogen group varies from one another. The size of  atoms  increases as we go down the group so the fluorine atom is the smallest one in the group and the iodine atom is largest.