Answer:
See explanation
Step-by-step explanation:
Electro negativity refers to the ability of an atom in a molecule to attract the shared electrons of a bond towards itself.
Electro negativity is a property of elements. It increases across the period and decreases down the group in the periodic table.
When two elements with differing electronegativities form a bond, the atom that has a greater electro negativity tends to pull the shared electrons of the bond towards itself. By so doing, there is greater electron density around that atom compared to the other atom. The more electronegative atom therefore acquires a partial negative charge while the other atom acquires a partial positive charge. This leads to a dipole in the molecule.
A molecule is said to be polar when it possess a dipole, that is, a positive end and a negative end. This phenomenon in turn arises when there is a significant difference in electro negativity between two atoms that compose the bond.
For instance, consider the formation of HF. Hydrogen has an electro negativity of 2.2 while fluorine has an electro negativity of 3.98. The difference in electro negativity between the both atoms is about 1.78. The molecule is polar with the negative end of the dipole at fluorine and the positive end at hydrogen.