The atomic-molecular structure of matter began to be actively studied by Lomonosov. The Russian scientist first applied a theory in chemistry, the essence of which was reduced to certain positions.
- All substances include "corpuscles" in their composition. This term Lomonosov called molecules.
- Corpuscles consist of "elements". Lomonosov used this term to designate atoms.
- All particles (both atoms and molecules) move continuously. The thermal state of all bodies is the result of the motion of the constituent particles.
- Same atoms make up molecules in simple substances, different atoms - molecules in complex substances.
Atomistic doctrine subsequently applied Dalton. The basis of the theory of the English scientist, characterizing the structure of matter, repeats the theory of Lomonosov. However, Dalton somewhat developed it. The English scientist tried to determine the atomic masses of the elements known at that time. In this case, Dalton denied the existence of simple substances of molecules, arguing that a simple substance contains only atoms. While complex elements include "complex atoms."
Finally, the theory of the atomic-molecular structure of substances was established only in the middle of the 19th century.
A molecule is called the smallest particle of matter. It has all the chemical properties of the element. Atom - the smallest particle, included in the composition of molecules of complex and simple substances. The composition of the atom determines the chemical properties of the elements. According to this provision, the modern definition of the smallest particle follows. Thus, the atom is an electrically neutral particle. It consists of a nucleus charged positively, and electrons charged negatively.
In accordance with modern concepts, the molecules make up vaporous and gaseous bodies. In solids, the smallest particles (molecules) are present under the condition of the presence of a crystal lattice, which, in turn, has a molecular structure.
There are several basic teachings.
The theory explaining the structure of matter indicates the presence of certain intervals between the particles. The dimensions of these distances depend on the temperature and the aggregate state of the object. The greatest gaps between the molecules are observed in gaseous bodies. This causes the ability of the gases to easily contract. Much less is the distance between molecules in liquids, so they shrink more difficult. Solids are practically not compressible, due to the fact that the spacing between the particles is small.
Molecules are constantly in motion. The higher the body temperature, the higher the speed of movement. Between the particles there are forces of mutual repulsion and attraction.
Molecules contain atoms that are also continuously in motion.
One kind of atoms is different from the other in properties and mass.
Substances of molecular structure in solid form have nodes of crystal lattices, which include molecules. The bonds between the particles are weak and burst when heated. Therefore, such bodies have low melting points.
Bodies can have another structure. Substances can consist of atoms and other particles that make up the nodes of the crystal lattices (for example, in iron, other metals). There are very strong links between these particles. To destroy them, it is necessary to spend a lot of energy. This structure of matter assumes a high melting point.
Many phenomena are explained on the basis of the teaching. For example, diffusion. This process is based on the ability of particles, molecules, atoms to penetrate into gaps that are present between atoms or molecules in another substance. This, in turn, is possible due to the constant movement of the particles that make up the body.