Atomic models are the structural aspects of atoms that have been presented by scientists in an attempt to better understand the atom and its composition.
In 1808, the English scientist John Dalton proposed an explanation for the property of matter. This is the first atomic theory that provides the basis for the currently known atomic model.
The constitution of the subject has been the subject of studies since ancient times. The thinkers Leucippus (500 BC) and Democritus (460 BC) formulated the idea that there is a limit to the smallness of particles.
They claimed that they would become so small that they could not be divided. This last particle was called an atom. The word is derived from the Greek radicals that together mean what cannot be divided.
Dalton’s Atomic Model
The Dalton Atomic Model , known as the billiard ball model, has the following principles:
- All substances are formed of small particles called atoms;
- Atoms of different elements have different properties, but all atoms of the same element are exactly the same;
- Atoms do not change when they form chemical components;
- Atoms are permanent and indivisible and cannot be created or destroyed;
- Chemical reactions correspond to a reorganization of atoms.
Thomson’s Atomic Model was the first to realize the divisibility of the atom. When researching cathode rays, the English physicist proposed this model which became known as the plum pudding model.
He demonstrated that these rays could be interpreted as a beam of particles charged with negative electrical energy.
In 1887 Thomson suggested that electrons were a universal constituent of matter. He presented the first ideas concerning the internal structure of atoms.
Thomson indicated that atoms should consist of uniformly distributed positive and negative electric charges.
He discovered this tiny particle and thus established the theory of the electric nature of matter. He concluded that electrons were constituents of all types of matter, as he observed that the electron charge / mass ratio was the same for any gas employed in his experiments.
In 1897 Thomson became recognized as the ” father of the electron .”
Rutherford Atomic Model
The model presented by Rutherford was perfected by Bohr. For this reason, the aspect of Bohr’s atomic structure is also called the Bohr Atomic Model or Rutherford-Bohr Atomic Model.
The theory of Danish physicist Niels Bohr established the following atomic conceptions:
- The electrons that spin around the nucleus do not spin randomly but describe particular orbits.
- The atom is incredibly small, yet most of the atom is empty space. The diameter of the atomic nucleus is about one hundred thousand times smaller than the whole atom. The electrons spin so fast that they seem to take up all the space.
- When electricity passes through the atom, the electron jumps into the next major orbit and then returns to its usual orbit.
- When electrons jump from one orbit to another, light results. Bohr could predict wavelengths from the constitution of the atom and the jump of electrons from one orbit to another.