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Law of Conservation of Mass
Antoine Lavoisier came up with the theory that mass cannot be created nor destroyed on this earth during a chemical reaction. -
Law of Definite Proportions
It was stated by Joseph Proust that the relative amount of an element within a compound is always equal. -
Atomic Theory and The Spherical Model
John Dalton joined the law of consevation of mass and the law of definite proportions to form his atomic theory. He said that; All Elements are made of indivisible and indestructible atoms, atoms of the same element are the same and atoms of different elements are not, and compounds always have the same relative number and kinds of atoms. He also proposed his spherical model which depicted that an atom cant be broken down. -
Discovery of the Proton
With the assistance of Rutherford, Eugene Goldstein discovered that there are protons in atoms. He came to this conclusion through an experiment where he used a tube similar to Thompson in 1897. -
Cathode Ray Experiment and Electrons
J.J. Thomspon conducted the cathode ray tube experiment to discover that electrons have a negative charge. He sent electricity through a cathode ray and proved the existance of electrons. Also developed the formula e/m = -1.76 x 108 coulombs/g. -
Quantum Theory
Theory based on using the idea of the unit for quantum to show the properties of subatomic particles and the interactions of matter and radiation. It was said by Max Planck, that energy can be emitted or absorbed by matter only in small units called quanta. -
Nuclear Model(Modified)
Ernest Rutherford created the model describing the atom as a tiny, positively charged core called a nucleus, in which nearly all the mass is located, around which the light, negative objects, called electrons, orbit around. -
Gold Foil Experiment and Nucleus
Ernest Rutherford conducted his famous experment known as the gold foil experiment. He fired particles at a thin sheet of gold foil to come to a conclusion that most passed through while a few deflected off. He discovered the nucleus, a small, dense central point of an atom. He also proposed his Nuclear Model, saying that electrons were orbiting around a central point in the atom. -
Bohr Model
Bohr made a suggestion that the electrons have to be orbiting the nucleus in certain set energy levels. The energy is givin out when electrons go from high energy to low. Also Bohr suggested that they could jump from one level to another. -
Quantum Mechanical Model
Erwin Schrodinger stated that the electrons were somewhat similar to waves. He created the Quantum Mechanical Model which demonstrated that electrons are found in a "blurry" cloud called the electron cloud. This model can also be referred as the electron cloud model. -
Uncertainty Principle
Werner Heisenberg came up with the theory that an electron's velocity and position cannot be known at the same time -
The Discovery of Neutrons
James Chadwick discoved the existance of neutrons in all atoms. Rutheford proposed the theory but his work was incomplete. He realized that electrons have no mass and figured out that something must give the atom mass.
