Answer:
high electronegativity difference between oxygen and hydrogen
Step-by-step explanation:
The electronegativity value of O and H are 3.5 and 2.1 respectively. The electronegativity difference of the O-H bond in H₂O is 1.4.
- When the elctronegativity difference between two atoms in bond is below 0.5 the bond is nonpolar covalent.
- When the elctronegativity difference between two atoms in bond is between 0.5 and 2.0 the bond is polar covalent.
- When the elctronegativity difference between two atoms in bond is above 0.5 the bond is ionic.
Thus the O-H is a polar covalent bond. This explains the polarity in water molecules.