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How do hydrogen bonds hold ice crystals together?

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A rough, translucent yellow crystal of elemental sulfur displayed against a solid black background. — crystal A crystal form of elemental sulfur. Sulfur has an atomic weight of about 32.06 atomic mass units (amu), which means that its molar mass is 32.06 grams.

In the crystal structure of ice, hydrogen bonds serve as the critical link between water molecules, maintaining the solid's lattice arrangement.12

A hydrogen bond occurs when a hydrogen atom, which is covalently bonded to a highly electronegative atom like oxygen, is positioned between that donor atom and another electronegative acceptor atom. Because the oxygen atom shares electrons unequally with the hydrogen, the hydrogen acquires a slight positive charge, while the acceptor oxygen atom possesses an unshared electron pair with a slight negative charge. This electrostatic attraction effectively "links" the oxygen atoms together.13

In ice, each oxygen atom is surrounded by four other oxygen atoms, with hydrogen atoms situated between them. These bonds form an open, hexagonal ring structure. While weaker than covalent or ionic bonds, these hydrogen bonds are strong enough to hold the crystal lattice together. When ice melts, some of these bonds break, causing the structure to collapse and the density to increase.243