Covalent bonds can be classified as nonpolar and polar covalent given the electronegativity difference between two atoms (ΔEN).
Nonpolar covalent bond electrons are shared equally between two atoms, polar covalent bond electrons are shared unequally, atoms have partial charges, ionic bond electrons are completely transferred to one atom, full charges present. Therefore, the greater the electronegativity difference, the greater the bond polarity. Let's determine the types of bonds present in the compounds and arrange the ones with polar covalent in order of increasing ΔEN. Sulfur and oxygen are both nonmetals so the substance is covalent. Sulfur has EN = 2.5 and oxygen has EN = 3.5. Since there is an electronegativity difference, the S−O bonds in the substance can be classified as polar covalent bonds.
