What is a polar covalent bond characterized by?

A polar covalent bond is characterized by unequal sharing of electrons between two atoms. This occurs when the atoms involved have different electronegativities, which is the ability of an atom to attract electrons in a bond. When one atom is more electronegative than the other, it attracts the shared electrons more strongly. This leads to a situation where the shared electrons are closer to the more electronegative atom, resulting in a partial negative charge on that atom, while the less electronegative atom gains a partial positive charge. This charge separation creates a dipole moment, giving the bond its polar characteristics.

In contrast, equal sharing of electrons describes a nonpolar covalent bond, where both atoms have similar electronegativity and thus share electrons equally. The complete transfer of electrons characterizes ionic bonds, where one atom donates electrons to another, leading to the formation of charged ions. Lastly, no sharing of electrons would refer to isolated atoms rather than a bond, making that option inapplicable. Hence, the distinguishing feature of a polar covalent bond is indeed the unequal sharing of electrons.