-
Period: 400 to
Past to present
-
450
Democritus Atomic Theory
The theory of Democritus claimed that everything is composed of "atoms", which are physically, but not geometrically, indivisible.That between atoms, there lies empty space; that atoms are indestructible, and always will be in motion,there are an infinite number of atoms, and kinds of atoms that have different shapes, and sizes.However, Democritus said "The more any indivisible exceeds, the heavier it is. This was very controversial. -
Antoine Lasvoisier
In 1774 Lasvoister proposed the oxygen theory of combustion. This was based on sound mass measurements.He also proposed the Law of Conversation of Mass which represents the beginning of modern chemistry.However to help with his work,he was associated with a tax-collecting firm and was married to the daughter of the one of the firm's executives. -
John Dalton Atomic Theory
Dalton proposed that different elements are composed of different atoms and that his theory was based upon the behaviour of the pattern. However he did not know what was in the atom and could not explain his theory. Furthermore Dalton's law states that the total pressure exerted by the mixture of non-reactive gases is equal to the sum of the partial pressures of individual gases. -
Dimitri Mendeleev
Today we use the periodic table to classify elements and are organized by atomic mass. However because of this scientist we would not have a proper periodic table. Mendeleev is know for creating and organizing the periodic table by it's atomic mass. This organization resulted in properties reapeating in a pattern or periodically well known as the periodic table -
Joeseph John Thomson
Thomson's atomic theory stated that he discovered electrons that consisted of negativley charged atoms and that there are 1840 electrons in an atom of hydrogen. He did provided evidence of this and did work by measuring the mass of the electrons and in 1911 his friend wilson and himself built a special camera that was needed in order to take a picture of it. -
Plum Pudding model
J. J. Thomson, who discovered the electron, proposed in 1904 before the discovery of the atomic nucleus in order to add the electron to the atomic model.This model, the atom is composed of electrons (which Thomson still called "corpuscles"),Now, at least part of the atom was to be composed of Thomson's particulate negative corpuscles, although the rest of the positively charged part of the atom remained somewhat unclear. -
Cathode Ray Tube
a vacuum tube containing one or more electron guns and a fluorescent screen used to view images.It has a means to accelerate and deflect the electron beam(s) onto the screen to create the images. J.J Thomson is known to use the CRT for his famous experiments and was abe to deflect cathode rays. The first cathode ray tube scanning device was invented by the German scientist Karl Ferdinand Braun in 1897. -
Robert Milikan Atomic theroy
In 1908 milikan conducted the oil drop experiment. This led him to determing the charge and masss of an electron.
He was able to measured the charge on a single electron. However. J.J. Thomson had already identified the charge-to-mass ratio of the electron. but, the actual charge and mass values were unknown. Therefore, if one of these two values were to be detected, the other could easily be determined. -
Ernest Rutherford,Rutherford model and Gold Foil experiment
Rutherford had done an exeriment called the gold foil experiment. When he would shoot something inside the atom the iteam would bounce back like if you were to shoot a bullet at it t would come back to you. Also it was Rutherford's interpretation of this data that led him to create the Rutherford model of the atom in 1911. He stated that a very small charge in the nucleus contained much of the atom's mass, and was orbited by low-mass electrons. He also theorized that neutrons exsits. -
Bohr Planetary Model
Bohr model was introduced by Niels Bohr in 1913. He described the atom as a small, positively charged nucleus surrounded by electrons that travel in circular orbits around the nucleus that is similar to the structure of the solar system, but with attraction provided by electrostatic forces rather than gravity. -
Henry Moseley
Henry Moseley a physicist discovered the empirical and chemical concept of the atomic number through Moseley's law in X-ray spectra. Moseley's Law explained many concepts in chemistry by organizing the chemical elements of the periodic table based on their characteristic and unique factor of the element in a logical order. -
Niels Bohr
Bohr had conducted essential contributions to the understanding of atomic strucutre and quantum mechanics. Bohr contributed to the atomic theory by broadening on Rutherford's earlier theory, Bohr published his theory which proposed that electrons travel in specific orbits around the nucleus, that outer orbits can grip extra elctrons than the inner orbits. -
Erwin Schrodinger and the Quantum mechanical model
In 1926 Erwin Schrödinger, updated the Bohr atom model by using mathematical equations to express the likelihood of finding an electron in a certain position. The atomic model is known as the quantum mechanical model of. In addition Schrodinger contributed to the atomic theory by discovering electrons moved in orbitals or shells around the nucleus -
James Chadwick Atomic Theory
Chadwick was awarded in 1935 Nobel Prize in physics for his discovery of the neutron. He was the head of the British scientists that were working on the Manhattan Project during World War II. He was achknowledged in England in 1945 for achievements in physics. -
Electron Cloud
Electron cloud is the region of negative charge surrounding an atomic nucleus that is associated with an atomic orbital. It is used to describe the area around an atomic nucleus where an electron will probably be. The electron cloud model was actually invented by four different scientists. They were Erwin Schrodinger, Ernest Rutherford, Niels Bohr, and Werner Heisenberg.
