Atom

Atomic Timeline

By mrdorkface(school)
  • 440

    Democritus (BC)

    Democritus (BC)
    Democritus believed atoms were small, hard particles. Called uncuttable particle atomos “not able to be divided”. (timetoast doesn't alllow BC years)
  • 440

    Aristotle (BC)

    Aristotle (BC)
    Aristotle diagreed with Democritus. He did not believe atoms could make up all things in nature. (Once again, TIme Toast has no BC dates)

  • Dalton (AD)

    Dalton (AD)
    He did expiriments about the atom. He discovered that all substances are made of atoms. Atoms cannot be created, divided or destroyed. Atoms of the same element are exactly alike. Atoms of different elements are different. Atoms join together to make new substances.

  • Mendeleev (AD)

    Mendeleev (AD)
    Mendeleev arranged the elements into a periodic table. Arranged elements by increasing atomic mass. Used the pattern of the periodic table to predict new elements.

  • Thompson (AD)

    Thompson (AD)
    Thompson determined that there are small, negatively charged particles inside an atom. An atom is a positive sphere with electrons mixed through it.

  • Moseley (AD)

    Moseley changed Mendeleev's periodic table by arranging the elements by number of protons. this corrected some flaws in Mendeleev's version.

  • Rutherford (AD)

    Rutherford (AD)
    Discovered that each atom has a small, dense nucleas, which is made of protons

  • Bohr (AD)

    Bohr (AD)
    Bohr discovered that electrons orbit the nucleas of an atom in a circular path, rather than just float around in the atom, as other scientists had thought.

  • Paragraph on Rutherford

    Paragraph on Rutherford
    He discovered that the atom has a small, dense, center called the nucleas. He discovered this by holding an expiriment usually referred to as the "Gold Foil Expiriment". During this expeiriment, he had 2 of his colleagues blast alpha particles at a very thin sheet of gold foil. Many of the alpha particles were redirected, and a few even shot back at the person firing the alpha particles. This completely disproved J.J. Thompson's theory that atoms were just empty space.

  • Answer to question

    Answer to question
    The atomic theory changed over time because new things were discovered, new were expiriments performed, and there was beter technology to obsereve the results with.