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Democritus (More, his theory)
This is Democritus' atomic theory ;
1.All matter consists of invisible particles called atoms.
2. Atoms are indestructible.
3. Atoms are solid but invisible.
4. Atoms are homogenous.
5. Atoms differ in size, shape, mass, position, and arrangement.
->Solids are made of small, pointy atoms.
->Liquids are made of large, round atoms.
->Oils are made of very fine, small atoms that can easily slip past each other. -
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Democritus
(About 460BC) He proposed the existence of an ultimate particle.His mentor, Leucippus, originally came up with the atomic theory, but it was then adopted by Democritus. The atomic theory stated that “The universe is composed of two elements: the atoms and the void in which they exist and move.” According to Democritus atoms were miniscule quantities of matter. Democritus hypothesized that atoms cannot be destroyed, differ in size, shape and temperature, are always moving, and are invisible. -
John Dalton's Atomic Theory
What did he do ?: He proposed his theory of atom linked to experimental evidence. He proposed the ''law of multiple proportions''.
His atomic model was a solid sphere model(or bowling ball model) -
Dalton (More)
Postulates
All matter consists of indivisible particles called atoms.
Atoms of the same element are similar in shape and mass, but differ from the atoms of other elements.
Atoms cannot be created or destroyed.
Atoms of different elements may combine with each other in a fixed, simple, whole number ratios to form compound atoms.
Atoms of same element can combine in more than one ratio to form two or more compounds.
The atom is the smallest unit of matter that can take part in a chemical reaction. -
Thomson's Atomic Theory
What did he do ?
He discovered the ''Plum Pudding'' atomic model. In 1897 J.J. Thomson discovered the electron, a negatively charged particle more than two thousand times lighter than a hydrogen atom. 1906 Thomson suggested that atoms contained far fewer electrons, a number roughly equal to the atomic number. -
Thomson (More)
The electrons must have been balanced by some sort of positive charge. The distribution of charge and mass in the atom was unknown. Thomson proposed a 'plum pudding' model, with positive and negative charge filling a sphere only one ten billionth of a metre across.
This plum pudding model was generally accepted. Even Thomson's student Rutherford, who would later prove the model incorrect, believed in it at the time. -
Ernest Rutherford's Atomic Model
What did he do ?: He proposed the ''Planetary''(or Rutherford) atomic model. He did the famous gold foil experiment by scattering alpha particles to the thin gold foil. -
Ruherford (More)
Planetary (or Rutherford) Atomic Model: The model described the atom as a tiny, dense, positively charged core called a nucleus, in which nearly all the mass is concentrated, around which the light, negative constituents, called electrons, circulate at some distance, much like planets revolving around the Sun. -
VIDEOS ABOUT MODELS
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The Modern Atomic Theory
The current theoretical model of the atom involves a dense nucleus surrounded by a probabilistic "cloud" of electrons. Electrons occupy regions of space whose shape is described by complex mathematical equations. -
SOURCE
http://www.scribd.com/doc/26307868/Democritus-Biography
http://www-outreach.phy.cam.ac.uk/camphy/nucleus/nucleus1_1.htm
https://www.boundless.com/physics/textbooks/boundless-physics-textbook/atomic-physics-29/the-early-atom-185/the-thomson-model-685-6307
http::/www.britannica.com/science/Rutherford-atomic-model
http://www.britannica.com/science/Bohr-atomic-model
http://www.mikeblaber.org/oldwine/chm1045/notes/Atoms/AtomStr2/Atoms03.htm -
Bohr's Atomic Theory
What did he do ?: He presented the 'Bohr Atomic Model''. The Bohr model of the atom, a radical departure from earlier, classical descriptions, was the first that incorporated quantum theory and was the predecessor of wholly quantum-mechanical models. The Bohr model and all of its successors describe the properties of atomic electrons in terms of a set of allowed (possible) values. Atoms absorb or emit radiation only when the electrons abruptly jump between allowed, or stationary, states.
