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Sep 4, 1500
BIBLIOGRAPHY of all sources
http://edtech2.boisestate.edu/lindabennett1/502/dalton.html
http://www.sparknotes.com/testprep/books/sat2/chemistry/chapter4section4.rhtml http://www.nobeliefs.com/atom.htm
http://profmokeur.ca/chemistry/history_of_the_atom.htm
http://www.timetoast.com/timelines/history-of-the-atomic-model--36 education.jlab.org/jsat/powerpoint/atomos.ppt
http://www.commonsensescience.org/atom_models.html
http://Galileo.phys.Virginia.EDU/classes/252/more_atoms.html
http://atomictimeline.net -
John Daltion
Dalton got most of his work based of the careful measurements of Antoine Lavoisier. Dalton realized that if elements were made up of atoms. And a combination of atoms are called a molecule. Dalton also came to the theory that atoms are indestructible and can not be cut anymore. From this point on, atomic theory is based off his findings. -
Dalton's Model
Dalton advanced atomic theory was by saying we had many different atoms out there and also revealed that you can not divide an atom into smaller pieces.
He came up with 4 theories that are still mostly true until now. -
Sir William Crookes
Discovered cathode rays had the following properties: travel in straight lines from the cathode; cause glass to fluoresce; impart a negative charge to objects they strike; are deflected by electric fields and magnets to suggest a negative charge; cause pinwheels in their path to spin indicating they have mass. -
J.J. Thomson
J.J. Thomson discovered that all atoms have electrons outside the nucleus. He discovered this by doing a series of experiements desgined to study the nature of electric discharge in a high-vacuum cathode-ray tube. Thomson electrically charged plates and magnets as evidence of "bodies smaller than regular atoms." This experiment helped him discover electrons and how they are in every single atom. -
J.J. Thomson's Model Plum Pudding Atomic Model
J.J. Thomson Makes His Atomic Discovery
In Thomson’s "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." The radius of the model was 10-10 meters.
Thomson suggested that the positive fluid held the negative charges, the electrons, in the atom because of electrical forces. However, this was only a very vague explanation and failed to provide any definite answers. -
Ernest Rutherford
Discovery Rutherford published his atomic theory discribing the atom as having a central nucleus (positive) surrounded by negative orbiting electrons. He found this out by doing an experiment with his gold foil model which contained a detecting screen (acting as the membrane), particle emitter, and silt. This model suggested that most of the mass n an atom was contained in a small nucleus. -
Rutherford Model
Rutherford tested Thomson's hypothesis by devising his "gold foil" experiment. He shot high velocity alpha particles (helium nuclei) at an atom then there would be very little to deflect the alpha particles. He decided to test this with a thin film of gold atoms. Most alpha particles went right through the gold foil but to his amazement a few alpha particles rebounded almost directly backwards. -
Niels Bohr
Niels Bohr applies quantum theory to Rutherford's atomic structure by assuming that electrons travel in stationary orbits defined by their angular momentum. This led to the calculation of possible energy levels for these orbits and the postulation that the emission of light occurs when an electron moves into a lower energy orbit. -
The Bohr Model
The Bohr Model Bohr applied the quantum theory to Rutherford's atomic structure by assuming that all electrons travel in stationary orbits defined by their momentum. This led to possible energy levels for their orbits. Bohr also developed his very own model of what an atom would look like with the nucleus and the electron lines. It is called the Bohr Model as you may know. -
The Quantum Mechanical Model Erwin Schrödinger.
Electrons are defined as standing waves. The electron probability distribution gives the areas in which the probability of electron presence is high. The exact position of the electron is never known as stated by the Heisenberg uncertainty principle:
Δx *Δ(mv) > h/4π
Where Δx is the uncertainty in a particle’s position. Δ(mv) is the uncertainty in a particle’s momentum. It is impossible to know accurately both the position and the momentum of as particle simultaneously. -
James Chadwick
James Chadwick discovered the neutrally-charged neutron. After a decade long struggle, Chadwick did a test on Beryllium and bombarded the element with alpha particles. This caused some of the protons to be discharged, creating neutrons.
