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350
Plato-five "Platomic solids"
He had came up with the theory of the existence of five kinds of regular solids.
To Plato at that time,these shapes were the only shapes that constituted perfect summetry within a non-planar set of points.
The name of these shapes are the hexahedron,tetrahedron,octahedron,icosahedron and the dodecahedron.
But it is not sure that if he is actually the first one who discovered the solids first.
Many people believe that Theaetetus,a friend of Plato,contributed this. -
420
Democritus-purposed the exist of atoms
He was the first person ever to propose that matter was made of atoms and that they are indestructible.He also theorized that they are,always and will be,in motion.
Democritus also had came up with the idea that the solidness of a substance would correspond with the shape and properties of the atoms involved. -
566
Aristotle-five kinds of atoms
Aristotle disbelieved the ancient Greek theory of atoms being of different sizes.
He held the view that there were five elements:
Fire-dry and hot
Water-moist and cold
Air-light
Earth-cool and heavy
Aether-divine Then he had been proven wrong in this area,though his theory was used for almost 2000 years until the scientific revolution when other theories prevailed. -
John Dalton-Dalton's atomic theory
The main points of Dalton's atomic theory:
1.Elements are made of extremely small particles called atoms.
2.Atoms of a given element are identical in size,mass,and other properties.
3.Atoms cannot be subdivided,created or destroyed.
4.Atoms of different elements combine in simple whole number ratios to form chemical compounds.
5.In chemical reactions,atoms are combined,seperated,or rearranged. -
J.J.Thompson-the structure of an atom and the thompson theory
He discovered the first subatomic particle-the electron.Then he realized that if there are negative-charged parts to atoms,there must be positive-charged parts as well because it theoretically should be balanced.(most matters are neutral.)
The Thompson atomic theory stated that atoms are uniform spheres of positively charged matter with electrons embedded. The theory was proposed around 1900 by Lord Kelvin and was heavily supported by Sir Joseph John Thompson -
Rutherford's atomic theory
He used his experimental data from several different experiment to conclude that the basic atomic structure was very different than that proposed by the Plum Pudding Model made by J.J.Thomson.
Rutherford proved that the model(an atom was made up electrons (the plums) surrounded by a positively charged mass (the pudding) is wrong.
He theorized that atoms were comprised of a very small necleus surrounded by elecrons. -
Niel Bohr-new model of the atom
The Niels Bohr atomic model was an improved model from the plum-pudding model and the rutherford model.
This version of model of the atom is very small,positively charged nucleus which contains proton and neutron surrounded by negatively charged electrons.
The model is basically considered as a primitive hydrogen atom model,it could be accepted as the derivation of a first order approximation of an atom of hydrogen using broader and much more accurate quantum mechanics. -
Binning&Rohrer-Invention of the STM
These two people invented the Scanning Tunneling Microscope known as the STM.The pair later received the 1986 Nobel Prize in physics.
The STM can be used not only to image atoms but to move them as well.
This invention speeded up other discoveries of atoms.