Collect information about various experiments conducted and theories proposed by scientists starting from John Dalton to Niels Bohr and prepare a story with a title "History of atom".

HISTORY OF ATOM

JOHN DALTON: from his experiments and observations, he suggested that atoms were very tiny particles and we cannot see it with our naked eye. Dalton believed that atoms were the fundamental building blocks of nature and could not be split. In chemical reactions.

J.J THOMSON: In 1898 J.J.Thomson discovered the electron. Thomson proposed a different model for the atom. He said that the tiny negatively charged electrons must be embedded in a cloud of positive charge like currants spread through a Christmas pudding.

ERNEST RUTHERFORD: In 1909, Ernest Rutherford performed the alpha particle scattering experiment. He said that Thomson's model could not be right. The positive charge must be concentrated in a tiny volume at the centre of the atom. On this model, the electrons orbited around the dense nucleus (centre of the atom).

ERNST RUTHERFORD

ERNST RUTHERFORD MODEL

NIELS BOHR: The next important development came in 1914 when Danish physicist Niels Bohr revised the model again and overcome the drawback of instability of atom in Rutherford model. Bohr suggested that the electrons must be orbiting the nucleus in certain fixed energy levels (or shells). The energy must be given out when 'excited' electrons fall from a high energy level to a low one.