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Dalton’s atomic theory or model based on the following postulates or assumption

1. All Matter made up of atoms are indivisible and indestructible.
2. All the atoms of a given element are identical atomic mass and properties.
3. Compounds are formed by the combination of two or more same or different kinds of atoms.
4. A chemical reaction is a rearrangement of atoms in the matter or compounds.

Rutherford and Bohr’s Atomic Structure

Science in chemistry education goes step by step and every scientist depends on the work of his predecessor. Therefore, this century Rutherford alpha ray scattering experiment has given valuable information about the nucleus of an atom and extranuclear electrons. Rutherford atomic model based on the following assumption

1. All the positive charge and the almost entire mass of an atom concentrated in a very small central core. He named this part as a nucleus of an atom.
2. The nucleus of an atom is surrounded by negatively charged particles carrying negligible mass, called electrons arranged in a definite structural arrangement.

Rutherford’s model does not conform to the classical model of electromagnetic radiation. When a moving charged particle will emit radiation, the particle loses kinetic energy and hits the nucleus. Therefore, Niels Bohr proposed the structure of hydrogen atom (one electronic atom) based on the following postulates.

1. An atom possesses several stable circular orbits in which an electron can stay. Therefore, this orbit or orbits is called energy level or hydrogen energy level where electron neighbor emits nor absorbed energy.
2. An electron can jump from one orbit to another with higher energy on the absorption of energy. From one orbit to another lower energy orbit with the emission of energy.
3. The angular momentum of an electron moving in an orbit is an integral multiple of h/2π.