A covalent bond is formed when two atoms share electrons. The nature of this sharing determines if the bond is polar or non-polar. This depends on the electronegativity of the atoms involved, which is their ability to attract shared electrons. Non-polar covalent bond: This type of bond forms when the two atoms sharing electrons have an equal or very similar electronegativity. This means the electrons are shared equally* between the atoms. As a result, there is no separation of charge, and no partial positive or negative poles are formed. Example:* In a molecule like $\text{Cl}_2$, both chlorine atoms have the same electronegativity, so the electron pair is shared perfectly equally. The electronegativity difference is zero. Polar covalent bond: This type of bond forms when the two atoms sharing electrons have a significant difference* in their electronegativity. The atom with higher electronegativity will attract the shared electrons more strongly, pulling them closer to itself. This creates a partial negative charge ($\delta-$) on the more electronegative atom and a partial positive charge ($\delta+$) on the less electronegative atom, forming a dipole. Example:* In a molecule like $\text{HCl}$, chlorine is more electronegative than hydrogen. The shared electrons spend more time closer to the chlorine atom, giving chlorine a partial negative charge ($\delta-$) and hydrogen a partial positive charge ($\delta+$). In summary: Non-polar covalent: Equal sharing of electrons, zero or very small electronegativity difference. Polar covalent: Unequal sharing of electrons, significant electronegativity difference.