Question

Which of the following carbon-halogen bonds is extremely polar though nonionic among given alkyl halides?
A) $C - F$
B) $C - Br$
C) $C - CI$
D) $C - I$

Answer 1

Carbon form bonds with halogens like fluorine, bromine, chlorine, and iodine. The polarity of these bonds depends on the electronegativity of the halogen. To solve this question we need to figure out the electronegativity order of the halogen. The halogen with the highest electronegativity will have the most polar bond.

Complete answer:
Halogens are one of the most electronegative elements in the periodic table. The tendency of atoms to attract pairs of electrons is called electronegativity. The Pauling scale is most commonly used to measure electronegativity. Fluorine (the most electronegative element) has a value of $4.0$ , chlorine has a value of $3.0$ , bromine and iodine have the value of $2.8$ and $2.5$ respectively.
We must remember that fluorine has the highest electronegativity of any given element. As already mentioned, the higher the electronegativity value obtained from an element, the more strongly the element attracts common electrons.
Now based on these facts, the order of polarity of the carbon-halogen bond is - $C - F > C - Cl > C - Br > C - I$ .
Hence the correct option is A) $C - F$ .

Note:
We can also know that there are some important exceptions to the above rules, including lanthanides, actinides, and noble gases. If the atoms in the table have the same electronegativity, both have the same tendency to attract pairs of electrons around them. We found this type of bond in ${H_2}$ or $C{l_2}$ molecules.