History of the Atom Timeline by Brooklyn Squiers and Skyller Castello

By brooklyn.squiers2017
  • 450

    Democritus (460 BC)

    Democritus (460 BC)
    Democritus started the idea of an atom.
    Democritus believed atoms were invisible particles of matter which vary in size, shape, and position.
    Democritus propsed a theory that matter can not be divided into smaller and smaller pieces forever. He came to this discovery by tearing a picec of paper into smaller and smaller pieces until it could not be torn anymore.
    Democritus's model of the atom was called the Solid, Invisible Sphere.
  • 450

    Aristotle (350 BC)

    Aristotle (350 BC)
    Aristotle believed all matter was made up of earth, fire, ice, and wind instead of atoms. Many scientists did not question Aristotle's beliefs due to his creatibility.

  • Dalton

    Dalton
    Dalton changed Democritus' theory by instead thinking all atoms were alike with the same atomic mass.
    Dalton proposed that all matter is made up of tiny indestructible particles called atoms. Inaddition, Dalton believed atoms could never be created or destroyed.
    Dalton came to this conclusion by using previous laws such as: Law of Conservation of Mass, Law of Constant Composition, and Law of Multiple Proportions.
    The name of Dalton's model is The Billard Ball.

  • Thompson

    Thompson
    (1856-1940)
    Thompson is the scientist cedited for discovering electrons.
    Thompson believed atoms were large bodies of a positive charge with negative parts dispersed throughout. Thompson knew electrons had a negative charge and thought matter must have a positive charrge.
    Thompson used a CRT(Cathode Ray Tube) to discover what he thought to be the mass and charge (negative) of an electron.
    Thompson's model is called "Plumb Pudding."

  • Rutherford

    Rutherford
    (1871-1937)
    Rutherford determined there was a small, dense nucleus with an overall positive charge.
    Rutherford also believed electrons orbited a positive center (nucleus) in a manner like planeets orbit the sun.
    Rutherford came to this conclusion by doing what is called the "Gold Foil Experiment." Rutherford shot alpha particles onto a gold piece of foil and noticed that most particles went through, but occasionaly an alpha particle veered of path.

  • Bohr

    Bohr
    (1885-1962)
    Bohr expanded further on Rutherford's theory by believing electrons lived on electron shells/orbitals. Bohr believed in 2 rules: electrons can only orbit a certain distance from the nucleus,and an electron can jump from one low energy level to a high energy level, causing the atom to absorb energy.
    Bohr later concluded that orbits have different shapes and can tilt in a magnetic field.

  • Heisenburg and Schrodinger

    Heisenburg and Schrodinger
    Harvey. "Atoms and the Periodic Table." Zachary High School. Feb. 2014. LectureSchrodinger and Heisenburg's work together created what is now know as the "Electron Cloud Model." Schrodinger believed electrons were actually waves. However, Heisenburg believed electrons were particles and they reside in what he called the Electron Cloud. Heisenburg and Schrodinger's opinions based the creation of the Quantom Theory. The Quantom Theory states that an electron appears in a wave-like "cloud" and has no definite position.

  • Citations

    http://www.nobeliefs.com/atom.htm
    http://atomtimeline.net/index.php
    http://www.ausetute.com.au/atomichist.html
    http://hi.fi.tripod.com/timeline
    Harvey, Nichole. "Atoms and the Periodic Table." Zachary High School. Feb. 2014. Lecture