The four types of crystals are distinguished and compared as follows:
1. Molecular crystals: molecular crystals are crystals made up of molecules through intermolecular forces (including van der Waals forces and hydrogen bonds). They usually have lower melting and boiling points because the intermolecular forces are weaker. Molecular crystals are less hard because the intermolecular forces are susceptible to external influences. For example, ice, organics, and hydrogen sulfide are molecular crystals.
2, ionic crystals: ionic crystals are crystals made of positive and negative ions combined by ionic bonding. They have higher melting and boiling points because of the higher strength of the ionic bonds. Ionic crystals are also harder because the ionic bonds are less susceptible to external influences. Common ionic crystals include salts, bases, and oxides.
3. Atomic crystals: atomic crystals are crystals made of atoms bonded together by *** valence bonds. They have very high melting and boiling points because the strength of the *** valence bonds is very high. Atomic crystals are also extremely hard because the *** valence bonds are very stable. For example, diamond, silicon, and germanium are atomic crystals.
4, metal crystals: metal crystals are crystals made of metal atoms and metal ions bonded by metallic bonds. They have higher melting and boiling points because the metal bonds are stronger. Metal crystals are also harder because the metal bonds are less susceptible to external influences. For example, copper, iron, and aluminum are metal crystals.
Applications of crystals:
1. Electronics and information technology: crystals are key components in the electronics and information technology industries. For example, semiconductor crystals are the basic material for manufacturing electronic devices such as integrated circuits, transistors, and solar cells. In addition, optical crystals are used in the manufacture of equipment such as lasers, optical instruments and optical fibers, providing the basis for the development of modern communications and information technology.
2, biomedical engineering: crystals also have a wide range of applications in biomedical engineering. For example, biocompatible material crystals can be used to manufacture artificial joints, prostheses and other medical devices to help patients restore their health. In addition, some crystals can be used as drug carriers to deliver drugs accurately and safely to the lesion site.
3, energy and environment: Crystals also have important applications in the energy and environmental fields. For example, crystals can be used to manufacture high-efficiency solar cells to support the development of renewable energy. In addition, some crystals can be used for environmental protection, such as removing harmful substances from the atmosphere.
4, material science and technology: Crystals have a wide range of applications in the field of material science and technology. For example, the study of crystal structure and properties can help us develop new materials with better performance. In addition, the properties of crystals can be used to create a variety of precision crafts, such as jewelry and watches.