-
John Dalton
He belived that All elements are composed (made up) of atoms. It is impossible to divide or destroy an atom.All atoms of the same elements are alike. One atom of oxygen is like another atom of oxygen. Atoms of different elements are different.An atom of oxygenis different from anatom of hydrogen.Atoms of different elements combine to form a compound.His theroy was called Daltons Atomic Theroy. -
Niels Bohr
Niels Bohr was a Danish physicist. He proposed a model of the atom that is similar to themodel of the solar system. The electrons go around the nucleus like planets orbit around the sun. All electrons have their energy levels – a certain distance from the nucleus. The energy of electrons goes up from level 1 to other levels. When electrons release (lose) energy they go down a level.When electrons absorb (gain) energy, they go to a higher level. -
J.J. Thompson
J. J. Thompson was an English scientist. He discovered the electron when he wasexperimenting with gas discharge tubes. He noticed a movement in a tube. He called themovement cathode rays. The rays moved from the negative end of the tube to the positive end. He realized that the rays were made of negatively charged particles electrons. -
Lord Ernest Rutherford
Ernest Rutherford conducted a famous experiment called the gold foil experiment. He used athin sheet of gold foil. He also used special equipment to shoot alpha particles (positively
charged particles) at the gold foil. Most particles passed straight through the foil like the foil was not there. Some particles went straight back or were deflected (went in another
direction) as if they had hit something.
