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100
The origin of Atomic Theory
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460
Democritus -
- Greek Philosopher born in 460 BC
- Created his own Democritus Atom Model
- His atomic theory states : everything is physically made up of atoms; invisible and can never be broken down; between atoms are empty spaces; more empty space the heavier the atom; atoms can never be destroyed or created
- His model didn't have a nucleus or electrons
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John Dalton
- best known for work in modern atomic theory
- proposed his atomic theory in 1803 : reasoned that tiny particles called atoms make up elements
- Dalton's law : total pressure exerted by the mixture of non-reactive is equal to the sum of the parttial pressures of individual gases
- devised the first atomic model called the solid sphere model
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J.J. Thomson
- discovered the electon in 1897, new theory that atom was made up of small particles and thus discovered electrons
- proved theory by using the cathode ray tube
- proved that atoms were made up of protons, electons, and nuetrons/ atom was divisible
- had a model called the plum pudding model
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Albert Einstein
- one of the fathers of modern atomic theory
- the theory of relativity
- Einstein's paper on Brownian Motion confirmed the atomic theory of matter; first prood that atoms actually existed
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Ernest Rutherford
- worked on radioactivity coining the terms "alpha" and "beta"
- was part of the GeigerMarsden experiment, existence of the atomic nucleus and this became part of his model of the atom
- his model was a symbol showing electrons circling around the nucleus often refered to as the planetary model
- 1908 was awarded the Nobel Prize in Chemistry
- element rutherfordium was named in his honor
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Neils Bohr
- Questioned the Rutherford atomic model 1913
- Bohr proposed the quantum theory of an atom; the model he created was called Bohr (Rutherford) Model
- Main points of the Bohr Model : electrons orbit the nucleus in orbits that have a set size and energy, energy of orbit is related to size, and lowest engergy is found in the smallest orbit
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Robert Millikan
- recipient of the 1923 Nobel Prize in physics
- worked on the elementary charge of electricity and on the photoelectric effect
- known for his oil-drop experiment that settled the argument and determined accurately both the charge and the masss of the electron
- this provided the first and most important proof of the new atomic theory
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Louis de Broglie
- French physicist that made groundbreaking contributions to quantum theory
- postulated the wave theory of electrons and suggested all mater has wave properties
- this concept is known as the wave-particle duality
- won the Noble Prize for Physics in 1929
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Werner Heisenberg
- created matrix mechanics, the first version of quantum mechanics
- memorable discoveries is the Uncertainty Principle : electrons do NOT travel in neat orbits; electrons that contian photons will change momentum and physics
- calculated behavior of electrons/subatomic particles
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Erwin Schrödinger
- developed model of the atom that combined equations for the behavior of waves with the de Broglie equation of create a mathmatical model for the distribution of electons in an atom
- his theory could be visualised while Heisenburg's was strictly math
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James Chadwick
- proved the existence of neutrons; before knew the existence of protons in the nucleus
- established atomic number is determined by the number of protons in an atom
- won the 1935 Nobel Prize in Physics
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Wolfgang Pauli
- Austrain physicist
- discovered an atom's electrons each have their own unique quantum state
- know as Pauli exlusion principle
- recieved the 1945 Nobel Prize in Physics
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Modern model of the atom
