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400
Democritus (460BC-370BC)
Democritus proposed that all matter (including space and time) was made up of tiny particles called "atoms". In Greek, the word "atom" means "indivisible", which makes sense because Democritus believed that "atoms" could not be seperated. Other Information:
- The Greeks (including Democritus) were more advanced back then compared to our society today.
- He was a very simple, Greek man. -
400
Aristotle (384-323BC)
Aristotle proposed that all substances are made up of the four elements: earth, water, fire, and air. Other Information:
- He believed that Earth was at the center of the universe.
- His beliefs on the atomic theory are FALSE.
- He developed the scientific method (a method of procedure that has characterized natural science since the 17th century, consisting in systematic observation, measurement, and experiment, and the formulation, testing, and modification of hypotheses). -
John Dalton (1766-1844AD)
Dalton proposed that all made up of tiny, indestructable particles called atoms. He also proposed that the atoms of the same element are identical and had the same mass and properties. Other Information:
- He elaborated on Democritus's ideas on atoms and formed what we know as the Atomic Theory. -
J. J. Thomson (1856-1940AD)
Thomson discovered the electron when experimenting with electric discharge in vacuum cathode-ray tubes. Other Information:
- He conducted something called the "Cathode-Ray Experiment".
- He made something called the "Plum Pudding Model" to display electrons in a space of positive material. -
Robert Millikan (1868-1953AD)
He experimented with an oil drop to determine the charge of a single electron. -
Ernest Rutherford (1871-1937AD)
Rutherford conducted the "Gold Foil Experiment" to discover the modern model of an atom. He found that all positive charges were located at the center of the atom, the nucleus, and all negative charges orbited the nucleus. -
Niels Bohr (1885-1962AD)
Bohr explained that outer orbits of an electron could hold more electric charges than inner orbits. With this information, someone could determine the chemical properties of an atom. Other Information:
- He found that electrons produce light by jumping through the orbits of an atom. -
Sir James Chadwick (1891-1974AD)
Chadwick discovered the neutron. He found that the neutron helps to balance the amount of protons in the nucleus of an atom.
