Hydrogen bonding is a strong type of intermolecular force that occurs when a hydrogen atom, covalently bonded to a highly electronegative atom like oxygen, nitrogen, or fluorine, is attracted to another electronegative atom nearby.

In water (H₂O), each molecule can form up to four hydrogen bonds with neighboring water molecules. This extensive hydrogen bonding network gives water many of its unusual and vital properties, including:

• High boiling and melting points compared to similar-sized molecules
• High surface tension, allowing insects to walk on water
• Density anomaly, where ice is less dense than liquid water, causing it to float
• Excellent solvent abilities, especially for ionic and polar substances

Hydrogen bonds also play critical roles in biological systems, helping to maintain the structure of DNA, proteins, and cell membranes. Thus, hydrogen bonding is a fundamental force shaping both the physical and biological world.