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500
Democritus and Leucippus suggest idea of the Atom.
Date: 500 BC
These Greek philosophers suggest the idea of a tiny, invisible particle called an atom. The reason behind the thought was nothing can come from nothing. -
Period: 500 to
Atomic Timeline
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Antoine Lavoisier establishes the Law of Conservation of Matter
The law states that, mass is niether created nor destroyed in any ordinary chemical reaction. -
John Dalton establishes the Spherical Model
The model showed how the atoms were seen as solid, indestuctible spheres, that when put together, made up all matter. -
Joseph Proust establishes Law of Definite Proportions
The law states that a chemical compound always contains exactly the same porportion of elements by mass. -
John Dalton discovers the Atomic Theory
The theory had four main parts.
1) All matter is made of atoms. Atoms are invisible and indestructible.
2) All atoms of a given element are identicle in mass and properties.
3) Compounds are formed by a combination of two or more different kinds of atoms.
4) A chemical reacyion is a rearrangment of atoms. -
J.J. Thomson completes the Cathode Ray Tube Experiment
The experiment demonstarted that electrons comprising cathode rays were nearly 2,000 times smaller in mass than the lightest know particle. -
Ernest Rutherford discovers the Proton
A proton is a positively charged elementary particle that is a fundamental constituent of all atomic nuclei. They were discovered by alpha particles being fired into hitrogen gas. -
Max Planck establishes Quantum Theory
It is a theory based on using the concept of the quantum units to describe the dynamic properties of subatomic particles and the interactions of matter and radiation. Energy can be emitted or obsorbed by matter only in small, discrete units called quanta. -
J.J. Thomson establishes the Plum Pudding Model
In the Plum Pudding Model each atom was a sphere filled with a positively charged fluid. The fluid was called the "pudding". Scattered in this fluid were electrons known as the "plums". He suggested that the positive fluid held the negative charges, the electrons, in the atom because of electric forces. -
Ernest Rutherford partakes in the Gold Foil Experiemnet
In the experiement he shot a beam of Alpha particles at a sheet of golf foil and it was found that a small percent of the particles were deflected. While a majority passed through the sheet. He concluded that a tiny, dense nucleus was causing the deflection and that this nucleus was were the mass of the the atom was concentrated. Nuclear Theory was established through the gold foil experiemnt. -
Ernest Rutherford establishes the Nuclear Model
Through the gold foil experiement, Rutherford uses the results to suggest that the atom consists of electrons oribiting arounf a very small, dense, positivley charged nucleus, which contained most of the atoms mass. -
Ernest Rutherford discovres the Nucleus
The nucleus of an atom is a dense region consisting of protons and nuetrons at the center of an atom. The Gold Foil Expeiement is what caused the discovery. -
Niel Bohr established the Bohr Model
The Bohr Model is a simpler planetary model like the earth orbiting arounf the sun. A light negatively charged electron moves in a circular orbit around a heavy, nearly stationary, positively chared proton. An attractive electric force holds the electrons in its orbit. -
Erwin Schrodinger establishes the Quantum Mechanical Model
The model states electrons are defined as standing waves. The electron probability distribution gives the areas in which the probability of electrons presence is high. It predicts were the electrons might be. -
Werner Heisenburg articulates the, Uncertainty Principle
The Uncertainty Principle states that, the posotion and velocity of an object cannot both be measured exactly at the same time, even in theory. -
James Chadwick advances the Nuclear Model
Chadwick confirms that nuetrons exist. Einstein, DeBroglie, SChrodinger and Heisenberg also help with the advances. These advances in the model state that, an atom has a nucleus that is surrounded by probability clouds. The clouds represent the most probable location of electrons. We still refer to these clouds as orbitals. The size and shapes of the orbitals may be calculated mathematically by using the equation for the waves. -
J.J. Thomson discovers the Electron
An electron is a ery small particle of matter that has a negative charge of electricity and that travels around the nucleus of an atom. It was discovered when Thomson was conducting experiments with beams of negative particles when he discovered that they consisted of lightweight particles with a negative charge. -
James Chadwick discoverd the Nuetron
Nuetrons are uncharged particles found within the Nuclei. The nuetron was discivered using radiation. -
Murray Gell-Man proposes a new quantum property
This property was called, "The Starngest Number". and with it he sorted particles into eight families called the eight fold way.
