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.
The theory applied by Rutherford is based on Newtonian physics. It is the theory that atoms are made up of the smallest particle and therefore can not be divided to a smaller size. An atom was the smallest unit of life.
"Bohr's doctoral thesis was concerned with the inadequacy of classical (that is to say, Newtonian) physics for describing the behavior of matter at the atomic level."
Ernest Rutherford developed his model in 1911 and it was called the Solar System model. It is the model most often taught in the earlier grades and states as follows; the atom is the smallest unit of matter. It has neutrons and protons in the nucleus, and electrons move around the outer shell. The protons have a positive charge, neutrons have a neutral charge, and electrons have a negative charge. The number of protons and electrons are the same. His theory stated that electrons would constantly be in a state of losing and regaining electrons meaning they were always unstable verses Bohr's theory that electrons have a stable time and an excited time.
Bohr developed the theory of quantum physics. In his theory there are also smaller units within the proton, neutrons, and electrons called quarks. An electron in its excited state has to fall back to a stable level. As long as electrons stay in their primary orbits they are in a stable state. Electrons give or take energy when they are in an excited state and the energy is released in packets called photons.