Being known that in atoms are electric charges, scientists were trying to formulate a model of the atom, considering that the atom must be electrically neutral.
The first atomic model was developed by W. Tleonsen and was developed by JJ Tleomson. The model assumes that the atom is composed from a sphere with the radius equal to the atom radius and the electrons distributed in the same area have the opportunity to be placed so that the atom to be electrically neutral.
Through experiences of appearance of charged particles on thin metal foil, Rutherford aimed to check the different atomic models proposed. These experiences have shown that positive charge is not equally distributed in atoms, but is concentrated in a volume of radius smaller than 10^-10 m in the nucleus.
Rutherford's experiments confirmed the planetary atom model in which positive charge of the atom is concentrated in a core with radius of about 10^-14m and electrons are revolving around it in orbits with radii of about 10^-14m.
To explain the structure of the atom, the Danish physicist Niels Bohr, developed in 1913, a theory known as "atomic Bohr'sTheory" . He assumed that electrons are arranged in layers or quantum levels, at a considerable distance towards the nucleus. This mode of arrangement is also called electronic configuration. The number of these electrons is equal to the atomic number.
Conventional, to the atom is assigned a planet system image, in which electrons are rotating around the nucleus as planets around the Sun. Since it can not be defined the snapshot position of an electron on orbit, in order to solve this uncertainty is assigned to the electron an electronically cloud form.
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