The Greeks already indicated the existence of fundamental particles, that they acted being constituent elements of the matter, predicting the existence of atoms of small size, and enumerating a small amount of different types from the same. Until the end of century XIX more data were not discovered on these elements. J.J. Thomson, next to other scientists, discovered in 1897 that the atoms were not indivisible as it were believed, but could be separated in small components. It discovered the composition of atoms and the existence of particles that they orbited in the outer zone called electrons, whose mass was much smaller than the one of the nucleus. The nucleus on the other hand, had positive charge and its weight almost supposed the totality of the atom. Although he was not able to determine the composition of the nucleus, the bases for later investigations were established, first of which they concentrated in the structure of the atom. The atom consists of a nucleus of great size on which they orbit electrons.
Rutherford was E. that it developed in 1911 a model based on a Solar System in miniature, in which the nucleus was a star (a sun) and the electrons the planets. The explanation of its theory had two errors: 1-that the electrons would emit energy when turning, reducing its speed which soon they would fall to the nucleus; erroneous because the electrons occupy fixed orbits. The second error consisted of which the electrons could jump of an orbit to another anyone around the nucleus.