Atomic Theory Timeline

Atomic Theory Timeline

1. The Greek philosopher Democritus was amog the first to suggest the existence of atoms.

   • In 300B.C. the popular philosopher Aristotle declared that all matter was made of only four elements: fire,air,water and earth.
     • In 1789 Antonie Lavoisier formulated the law of conservation of mass, which states that the mass of the products of a reaction is the same as the mass of reactants.
       • In the early 1800's, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms.
         • In 1897, the English scientist named J.J Thomson provided the first hint that an atom is made of even smaller particles.
           • In 1908, the English physicist Ernest Rutheford performed an experiment using positively charged particles fired at gold foil.
             • In 1913, the Danish scientist Niels Bohr proposed an improvment. He built on the concept that the mass of an atom is contained mostly in the nucleus.
               • Right now in the 20th scientist developed the Modern Cloud Theory which is used today.