Festkörper

Festkörper, also known as solids, are one of the fundamental states of matter, distinct from liquids, gases, and plasma. In a solid, atoms and molecules are held tightly together in a fixed arrangement, vibrating about their equilibrium positions. This close packing and strong intermolecular forces are responsible for the characteristic properties of solids, such as their definite shape and volume. Unlike liquids, the constituent particles in a solid cannot move past one another freely, which is why solids resist changes in their form.

There are two main categories of solids: crystalline and amorphous. Crystalline solids possess a highly ordered, repeating three-dimensional structure known as a crystal lattice. Examples include common salt (sodium chloride), diamond, and metals. This ordered structure gives crystalline solids sharp melting points. Amorphous solids, on the other hand, lack long-range order in their atomic arrangement. Their particles are arranged more randomly, similar to liquids, but are still held in fixed positions. Glass, rubber, and many plastics are examples of amorphous solids, which tend to soften over a range of temperatures rather than melting abruptly.

The properties of solids depend greatly on the nature of the bonding between their constituent particles. Ionic solids, like table salt, are formed by electrostatic attraction between positively and negatively charged ions. Covalent solids, such as diamond, feature strong covalent bonds extending throughout the entire structure. Metallic solids, like copper, consist of a lattice of metal atoms where valence electrons are delocalized, forming a "sea of electrons" that accounts for their conductivity. Molecular solids are held together by weaker intermolecular forces, such as Van der Waals forces or hydrogen bonds.