What happens to metals under pressure, in terms of atomic structure?

Metals are characterized by a unique atomic structure that includes a sea of delocalized electrons surrounded by positively charged metal ions. When pressure is applied to metals, this arrangement allows the layers of atoms to slide past one another without breaking the metallic bonds, which is a property known as ductility. This sliding is a fundamental reason metals can be shaped and deformed without shattering. The ability of the atomic layers to move past each other is crucial for the malleability and ductility observed in metals.

The sliding of layers under pressure does not disrupt the metallic bonding significantly, as these bonds are not covalent or ionic but rather a result of electromagnetic forces among the free electrons and the metal ions. This feature of metals contrasts with other materials, such as ceramics or some covalent compounds, which tend to fracture under similar pressures due to their rigid structures.

The other options do not accurately describe the behavior of metals under pressure. While applying pressure might influence various properties of metals, the key characteristic is the ability of atomic layers to remain intact while allowing movement, which is why sliding layers is the correct answer.