Concentric circles

Saher Tariq

By psharmaims
  • 460 BCE

    Democritus

    Democritus
    Some information in Democritus's theory was that all matter consists of invisible particles called atoms. Atoms are indestructible. Atoms are solid but invisible. Atoms are homogeneous. Atoms differ in size, shape, mass, position, and arrangement. Democritus never had the right equipment to test his theory so his theory was neglected.

  • John Dalton

    John Dalton
    In Dalton's theory he said matter is made up of atoms that are indivisible and indestructible. He also said all atoms of an element are identical. He said atoms of different elements have different weights and different chemical properties. He said that atoms of different elements combine in simple whole numbers to form compounds.
    Lastly, he said atoms cannot be created or destroyed, and when a compound decomposes, the atoms are recovered unchanged.

  • J. J. Thompson

    J. J. Thompson
    J. J. Thomson discovered the electron when he was experimenting with gas discharge tubes. when doing the experiment he noticed movement in the tube. He called this movement cathode rays. The rays moved from the negative end if tube to the positive end of tube. He realized that the rays were made of negatively charged particles - electrons.

  • Lord Ernest Rutherford

    Lord Ernest Rutherford
    Rutherford conducted an experiment called the gold foil experiment. He used a thin sheet of gold foil and special equipment to shoot positively charged alpha particles. Most particles went straight through, other particles went straight back or were deflected as if they hit something.
    He discovered that atoms are made of small positive nucleus; positive nucleus pushes away positive alpha particles. Also, he said that atoms are mostly empty space.

  • Niels Bohr

    Niels Bohr
    Bohr proposed a model of an atom that was similar to the model of the solar system. I his model he showed that the electrons go around the nucleus like planets orbit the sun. All electrons have their energy level - a certain distance from the nucleus. Each energy level can hold a certain amount of electrons. Level 1 can hold 2 electrons, Level 2 can hold 8 electrons, Level 3 can hold - 18 electrons, and level 4 can hold 32 electrons.