Question

Are $B - F$ and $B - I$ polar?

Answer 1

Due to the repulsive force between particles of the same nature, there is charge separation. This is called polarity. Polarity results in the formation of molecular and ion dipole moments. Therefore, molecules are classified into polar molecules and nonpolar molecules according to their polarity. The polarity or nonpolarity of any compound or molecule can be defined in terms of electronegativity.

Complete Step By Step Answer:
We know that according to polarity, molecules can be divided into two parts: polar molecules and nonpolar molecules. Polar molecules are those molecules that have a net dipole moment due to the electronegativity difference of the atoms in the molecule, and dipoles are not allowed to cancel out, while non-polar molecules are those molecular atoms with a net dipole moment of zero The dipoles cancel each other out in the molecule. The study of polarity is important because it defines several physical properties of the molecule, such as melting point, boiling point, dipole moment, and solubility. It is governed by the principle of electronegativity. Different atoms have different electronegativity, which causes shared pairs of electrons to attract each other in different amounts.
Atoms like F,O,N have a very large amount of electronegativity and they attract the electrons towards themselves. This leads to the uneven charge distribution thus leading to the polar bond.
Non-polar bonds are formed when the difference in the electronegativities of atoms is less than $0.5$ and polar bonds are formed when the difference in the electronegativities of atoms is more than $0.5$ .
In $B - F$ , the electronegativity of B is $2$ and that of F is $4.$ The difference between their electronegativities is greater than $0.5$ . Therefore, it is a polar molecule.
In $B - I$ , the electronegativity of B is $2$ and that of I is $2.5.$ The difference between their electronegativities is greater than $0.5$ . Therefore, it is a nonpolar molecule.

Note:
Polar bonds have a net dipole moment and are usually formed when there is no symmetry in the molecule. Without symmetry, the dipole moments of different atoms will not cancel each other out, resulting in a net dipole moment. Non-polar bonds do not have any net dipole moment and are usually formed in compounds with symmetry.