The type of bond that has unequal sharing of bonding electrons is called a polar covalent bond.
In a polar covalent bond, the electrons shared between the two atoms are not distributed equally. This occurs because the two atoms involved in the bond have different electronegativities, which is a measure of an atom’s ability to attract and hold onto electrons. When one atom is more electronegative than the other, it will attract the shared electron pair more strongly, resulting in a partial negative charge on that atom and a partial positive charge on the other atom. This unequal distribution of electron density creates a dipole moment, which is characteristic of polar molecules.
For example, in a water molecule (H2O), the oxygen atom is more electronegative than the hydrogen atoms, leading to a polar covalent bond. As a result, the oxygen atom carries a slight negative charge, while the hydrogen atoms carry slight positive charges. This polarity is important for the unique properties of water, such as its high surface tension and ability to dissolve many substances.