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100
Aincent China
The Aincent Chinese people used to believe that there are 5 basic elements which are fire, water, wood, metal and earth. -
100
Ancient Greece
The residents of Aincent Greece used to think that there are 4 basic elements; Fire, Water, Earth and Air. -
400
Democritus 400 B.C.E.
Democritus suggested that rocks could be crushed and broken into bits that can no longer be minimized in size. -
John Dalton
Dalton suggested that all matter is made of small particles called Atoms which are like small spheres but with different properties. They may differ in size, shape and color. All atoms of an element are identical is in size and mass. Different elements have different properties. Different atoms can be combined to create new substances. He also created our first periodic table. -
J.J. Thompson
He discovered Electrons in 1897 with his cathode ray experiment. -
Ernest Rutherford
He conducted a experiment in which the high speed positive particles went right through the foil. 1 in 10,000 particles bounced back as if deflected by something positively charged and massive. Rutherford had discovered the Nucleus. He compared and calculated, ending with the result that the size of a nucleus is like a pea in a football field. He discovered that an atom's mass is mostly the nucleus and that the nucleus is positively charged. He found out that Electrons run in a fixed orbit. -
J.J. Thompson
He also discovered Isotopes in 1913. -
Niels Bohr
He discovered that the Nucleus surrounded by orbiting electrons at different energy levels and that Electrons have definite orbits. -
Ernst Schrödinger & Werner Heisenberg
They discovered that Electrons are in probability zones called Orbitals. Electrons are particles and waves at the same time. They also developed Quantum Numbers based on Albert Einstein and Planck's theory. -
James Chadwick
James Chadwick (Rutherford's student) discovered the neutrons.
