Which covalent bond involves a pair of electrons being shared unequally, resulting in partial charges on the atoms?

• A. Covalent Bonding
• B. Nonpolar-Covalent Bond
• C. Ionic Bonding
• D. Polar-Covalent Bond

Answer: (D)

When two atoms form a covalent bond, they share electrons. The way those electrons are shared depends on how strongly each atom attracts them, i.e., their electronegativities. If the atoms have similar electronegativities, the shared electrons spend roughly equal time around each nucleus, leading to a nonpolar covalent bond with no significant partial charges. If the electronegativity difference is larger, the more electronegative atom pulls the electrons closer, creating an unequal sharing scenario. This produces a polar covalent bond with partial charges: the more electronegative atom carries a partial negative charge, while the other atom carries a partial positive charge. Ionic bonds, in contrast, involve complete transfer of electrons and the resulting ions, not partial charges within a bond.

So the bond described—covalent but with unequal sharing and resulting partial charges—is polar covalent. Water’s O–H bonds and hydrogen chloride’s H–Cl bond are common examples where this unequal sharing creates a dipole moment due to partial charges.