Rutherfords Atomic Model

Show/Hide Page Index This model is also called “Nuclear atomic model” or “planetary model of atom”. This model is given in the year of 1911 by British Physicist “Ernest Rutherford”. According to the Rutherford’s atomic model, the atom consists of a core which is at the center of atom. This core is called Nucleus of atom. Almost the all mass of an atom is concentrated in this nucleus. This nucleus is positively charged & is surrounded by tinny light negatively charged particles, which are called “electrons”.

These electrons circulate around the nucleus in the same manner such as planets circulate around the sun in planetary system. That is why, this model is also referred as “planetary model of atom”. The radius of nucleus is about 10-13 cm. The radius of circular path travelled by electrons around the nucleus is about 10-12 cm which is greater the diameter of electron. The radius of the atom is about 10-8 cm. Thus the, like a planetary system, the atom is also of exceedingly open nature, due to which it can by penetrated by high speed particles of various kinds. The “Rutherford’s planetary atomic model’ is shown in figure below- A force of attraction exits between positively charged nucleus & negatively charged electrons travelling around the nucleus. This electrostatic force between positively charged nucleus & negatively charged electrons is similar to the gravitational force of attraction between Sun and planets revolving around the sun. Most of the part of this planetary atom is open space, which does not offer any resistance for passes of positively charged tiny particles such as Alpha particles.

Nucleus of atom is very small, dense & positively charged which results in the scattering of positively charged particles. This phenomenon for scattering of positively charged alpha particles by positively charged nucleus, explains the scattering of positively charged alpha particles by gold foil as observed in a series on experiments by Ernest Rutherford. The Ernest Rutherford atomic model succeeded to replace the atomic model “Thomson’s Plum Pudding model” given by English Physicist “Sir J.J. Thomson”

According to The Ernest Rutherford’s atomic model, the electrons are not attached to atom. The electrons are either stationary or rotates in circular paths around the nucleus. But if the electrons are stationary they must be fallen to nucleus due to attraction force between electron & nucleus On the other hand if the electrons are moving in a circular path, than according to electro-magnetic theory, the accelerated charge of electron would have continuously lost its energy and would have down into the nucleus as shown in figure below- Thus, the deficiencies of Rutherford’s Atomic model can be described as below-

1. The Rutherford’s atomic model does not explain the distribution of electrons in the orbits.
2. The Rutherford’s atomic model does not explain the stability of the atom as a whole.

The above drawbacks of Rutherford’s atomic model were overcome by Bohr’s atomic Model (1913).