Why does ice float?
Molecular geometry describes the three-dimensional arrangement of atoms. Electron-pair repulsions provide a remarkably useful first model for many main-group molecules.
The short answer
Molecular geometry describes the three-dimensional arrangement of atoms. Electron-pair repulsions provide a remarkably useful first model for many main-group molecules.
What is really happening?
Molecular geometry describes the three-dimensional arrangement of atoms. Electron-pair repulsions provide a remarkably useful first model for many main-group molecules.
Shape matters because it influences polarity, intermolecular interactions and ultimately many physical and chemical properties.
Chemical bonding describes how atoms are held together through interactions involving electrons and nuclei. Ionic, covalent and metallic models highlight different limiting behaviours rather than three completely isolated worlds.
A useful mental picture
Water is unusual: its hydrogen-bonded solid structure is more open than liquid water, so ordinary ice is less dense and floats.