# Introduction Of Atomic Physics And The Contributions Of Scientists To Atomic Physics

In this resource, a complete glance on atomic model is explained. This resource gives the explanation about the history of atom in gradual manner. In this resource, we can observe the contributions of scientists towards atomic physics with their postulates.

## Introduction of atomic physics

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We can understand the topic of atomic physics by discussing about the term i.e., atom. The word atom is derived from Greek world which leterally means indivisible. In 1803 Daltlon put forward his theory about atom according to this theory atom is indivisible neutral particle. The failure in Daltons' model of atom was that it could not explain how electricity could interact with matter. First time, Michael Faraday studied the passage of electricity through liquid solutions. In his laws of electrolysis, he established that matter is electrical in nature. In other words we can say that matter is composed of positively charged particles and negative charged particles.

In 1870, William Crooke, in his experiments, about discharge of electricity through gases which led to the discovery of cathode rays. He said that cathode rays consist of streams of negatively charged particles. Further, electrical nature of matter was made by J.J.Thomson in 1897. His studies on electrical discharge through gases at low pressure established that atom is divisible. These studies of electrical discharge through the gases and discovery of cathode rays marked the beginning of an entirely new branch of physics.

Already it is assumed that atom as a whole is electrically neutral. Therefore, the total positive charge and negative charge in an atom must be exactly equal. This stability in the atom has led to distribution of charges in the atom. J.J.Thomson proposed a model for the internal structure of an atom.

According to J.J.Thomson model, an atom consists of positively charged core with electrons uniformly distributed over by it like seeds in a watermelon. But, this model is not successful because this model could not explain spectral lines of Hydrogen atom.

A different description about the atom is proposed by Rutherford that the experiments on scattering alpha particles from gold foils. Rutherford concluded that the entire positive charge and mass of an atom resides in a tiny place called nucleus and electrons revolve around the nucleus. Rutherford's model had also failure because when electron revolves around the nucleus, then after some time it looses energy finally fall in the nucleus. This happens regarding concept of electrodynamics.

This failure is covered by Bohr in his postulates that electrons can only orbit in certain privileged orbits called stationary orbits, in these orbits no electron radiates energy. This theory was successfully applied to Hydrogen atom. In second postulate of Bohr that the stationary orbits are fixed by the angular momentum of the electron should have the value is integral multiples of h/2pie.

The orbiting electron can jump to higher orbit if it absorbs energy, on other hand, the orbiting electron can jump to lower orbit if it looses energy. That energy is equal to hv, where h is Planck's constant and v is the frequency of radiation. But Bohr's theory could not explain the spectral lines of Hydrogen atom have electrons more than one.

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