Atomic Theory

By SigridKim
  • 400 BCE

    Democritus (400 B.C.)

    Democritus (400 B.C.)
    • Democritus lived in Abdera and lived from 400 B.C. to 370 B.C.E
    • He was the first one that stated the idea of atoms. He discovered that if a substance was repeatedly divided into smaller parts until it cannot be divided any further.
    • What Democritus did to find the information, was that he broke a shell into half and kept going until he couldn't go any further.
    Interesting Fact: Democritus' father was from a noble family. Source:
    https://www.iep.utm.edu/democrit/

  • John Dalton (1808)

    John Dalton (1808)
    • John was a school teacher in England from 1766 to 1844.
    • John found out that new substances were in mathematical ratios; which is now known as the atomic mass on the periodic table.
    • John found this new information by examining chemical reactions and carefully measured the weight and mass of them.
    Interesting Fact: John was born in a Quaker family. SourceL
    https://www.britannica.com/biography/John-Dalton

  • JJ Thomson (1897)

    JJ Thomson (1897)
    • Thomson found out that atoms contained negatively charged particles in 1897; which is called electrons.
    • Thomson was born in Cheetham Hill, Manchester in 1856.
    • Thomson found out about electrons by using the raisin bun model, which is where the dough of bun is the positively charged ball and the raisin was the negative charge.
    Interesting Fact: In 1890, Thomson married Rose Elisabeth. Source: https://www.nobelprize.org/prizes/physics/1906/thomson/biographical/

  • Ernest Rutherford (1911)

    Ernest Rutherford (1911)
    • Ernest discovered that atom is mostly empty space in 1911.
    • Ernest lived in Spring Grove, New Zealand in 1871 and passed away in 1937 at Cambridge.
    • Ernest did multiple experiments that included shooting a beam of particles towards a gold foil.
    • Because Ernest has done these experiments, he was able to tell the world that the atom is mostly empty.
    Interesting Fact: Ernest's mother's name is Martha Thomson. Source: https://www.britannica.com/biography/Ernest-Rutherford

  • Niels Bohr (1913)

    Niels Bohr (1913)
    • In 1913, Niels used Ernest's experiments to show that electrons move around the nucleus at specific energy levels depending on how much energy they contain.
    • Niels lived in Copenhagen in 1885.
    Interesting Fact: Niels' discovery about the atoms came with a Nobel Prize in 1922. Source: https://www.nobelprize.org/prizes/physics/1922/bohr/biographical/