A massive iron cube with an edge length of 25 mm contains about a quadrillion (10 24) atoms! This corresponds approximately to the number of 1-litre-milk-bags that would be needed to fill the entire volume of the earth with milk! Unit cell The lattice constant is on the order of about 250 to 500 pm. The distance between two ions is a characteristic value for the corresponding metal and is called a lattice constant. Therefore, the atomic distance of two neighboring ions will not correspond exactly to the value obtained in the figure above with only two atoms. The whole particles thus influence each other in their electrostatic effect. The individual particles then perceive not only the repulsive forces of their immediately adjacent particles but also the forces of particles located further away. Of course, a metal consists not just of two atoms, but of a multitude of particles. Finally an equilibrium state is reached, in which both forces are equal and a resultant force disappears. If the approach is too close, however, the repulsive force is greater, so that the distance increases again. If the distance between the two ions is reduced, the repulsive force increases more and more and rises disproportionately compared to the attracting effect. At a large distance, the attractive force of the electron gas predominates, so that the ions initially approach each other. The animation above shows the forces acting between two ions. Materials lacking such a crystalline structure are called amorphous! A typical example of an amorphous material is glass, but many plastics also have an irregular atomic structure.Ī regularity in the atomic structure of a substance is called crystal structure or lattice structure. Substances lacking such a crystalline structure are called amorphous.
Figure: Acting forces on the metal ionsĪ crystalline structure is a typical feature of metals. The substance itself is called crystalline. However, the grid structure can take different forms, which will be discussed in more detail in the article Important types of lattice structures. Such regularity in atomic structure is also referred to as crystal structure or lattice structure. This ultimately leads to a regular build-up of the atomic structure. In this stable position the cations keep a fixed distance. The electron gas thus tries to approach the various cations, while the cations themselves repel each other.Ĭonsequently, there is an state of equilibrium in which both forces compensate each other. On the other hand, there are repulsive forces between the cations themselves due to their identical charges. On the one hand, there are attractive forces between the positively charged ions and the negatively charged electron gas.
Lattice meaning free#
Due to the released electrons, a kind of “gaseous” state of the free electrons is formed around the positive ions. In this way, positively charged metal ions remain (cations). The metal atoms release all their outer electrons and thus reach the noble gas configuration. The structure of metals has already been explained shortly in the chapter on metal bonding. Due to this special position of metals in mechanical engineering, their atomic structure is discussed in more detail below. In addition, metals have a very good thermal conductivity and electrical conductivity, which gives these materials a wide range of applications. Compared to other materials, they can withstand relatively high loads, but still have sufficient plasticity (ductility) not to break immediately under stress.
Metals play an important role in mechanical engineering.
0 kommentar(er)
