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Law of Conservation of Mass
In 1789, Antoine Lavoisier proposed the theory that mass is iniether created nor destroyed during a chemical reaction. -
Period: to
Timespan of the atomic timeline
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Law of Definite Proportions
Joeseph Proust stated that the relative amount of each element in a particular compound is always the same, regardless of the preparation or source -
Atomic Theory and Spherical Model
John Dalton linked the law of consevation of mass and the law of definite proportions to form his atomic theory. he stated that: All Elements are composed of indivisible and indestructible atoms, all atoms of the same element are identical and atoms of different elements are different, compounds always have the same relative number and types of atoms,and chemical reactions involve only a rearrangement of atoms. He also proposed his spherical model which depicted that an atom cant be broken down. -
Who discovered the Proton?
Eugene Goldstein, along with rutherford, discovered the proton in cells. He made this discovery by using a hydrogen gas-filled tube, which was similar to Thompson's tube in 1897. -
Cathode Ray Experiment and the Electron
J.J. Thompsoncarried out a cathode ray experiment. by sending electricty through a cathode ray, he proved that these small cathode ray particles must be negative since they were attracted to the positive pole. He called these particles electrons. At the time, electrons were neutral subatomic particles embedded within the nucleus. Thompson resembled this is his Plum Pudding Model -
Quantum Theory
Theory based on using the concept of the quantum unit to describe the dynamic properties of subatomic particles and the interactions of matter and radiation. It was postulated By Max Planck, that energy can be emitted or absorbed by matter only in small, discrete units called quanta. -
Gold Foil Experiemant and the Nucleus
Ernest Rutherford conducted his famous experment known as the gold foil experiment. he fire alpha particles at a sheet of gold foil to discover that most passed through while some where deflected. he discovered the nucleus, a small, dense central point of an atom. He also proposed his nuclear model, stating that electrons were distributed around a central core of an atom, the nucleus. -
Modified Nuclear Model
Rutherford and Chadwick stated that it is protons and neutrons in the nucleus orbited by electrons in the elctron cloud -
Bohr Model
Niels Bohr predicted that the electrons moved in specific circular paths, or orbits, at different levels of different energy amounts. He also said that the electrons can jump from one level to another. -
Quantum Mechanical Model
Erwin Schrodinger stated that the moving particles, electrons, were similar to waves. He developed the Quantum Mechanical Model which illustrated that electrons are found with a "blurry" cloud called the electron cloud. This model is also know as the electron cloud model. -
Uncertainty Principle
Werner Heisenberg proposed the theory that an electron's position and velocity cannot be simultaneously known -
Who discovered the neutron?
Since electrons have almost no mass, it seemed like something else was adding to the mass of the atom. In a helium example James Chadwick used, there would be four protons and two electrons in the nucleus to yield a mass of 4 but only a charge of 2! He also put out an idea that there could be a marticle with mass but no charge, naming it the neutron.
