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460 BCE
Democritus
He stated that matter is made up of tiny individual particles called atoms. Atoms could not be created, destroyed or further divided. -
460 BCE
Democritus Atomic Model
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Dalton’s Atomic Theory
- Matter is made up of any particles called atoms - indivisible and indestructible.
- Atoms of a given element are identical in size, mass, and chemical properties. Different from different elements.
- Atoms of two or more different elements combine to form compounds. A particular compound is always made up of the same kind of atoms and in the same proportions.
- A chemical reaction involves the rearrangement, separation, or combination of atoms.
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Dalton Atomic Model
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Thomson Atomic Model
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Thompson´s Experiment
Applied electricity to a glass tube and produced streams of small particles called cathode rays. Then, particles must be negatively charged, they were called electrons. -
Thompson’s Model
Atoms are neutral, thus the sphere contains the same quantity of positive and negative charges. Also, discovered the electrons. -
Rutherford’s Model
Atoms consisted mostly of empty space through which the electrons move. Almost all positive charge and mass were contained in a dense region in the center: the nucleus. -
Rutherford Atomic Model
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Rutherford´s Exepriment
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Bohr’s Model
Developed an explanation of atomic structure that underlies regularities of the periodic table of elements. His atomic model had atoms built up of successive orbital shells of electrons. Atoms have only certain allowable energy states. -
Bohr’s Atomic Model
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James Chadwick’s Model
Using alpha particles discovered a neutral atomic particle with a mass close to a proton. Thus he discovered the neutron. -
Chadwick’s Atomic Model
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Schrödinger’s Model
Electrons can be found in a particular volume of space around the nucleus.
Atomic orbital — Region around the nucleus that describes the electron ́s probable location.
Electrons are treated as waves. -
Schrödinger’s Atomic Model
