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The Atom & Radiation

History of the Atom and Radiation

What are the three ideas that Democritus proposed? 1. Atoms bounce off each other when they collide 2. Have velcro-like hooks on thier surfaces that allow them to stick together 3. Change is the result of atoms recombining, not new ones being formed
What are the four ideas Dalton proposed? 1. Atoms are fundamental, indivisible, and invisible 2. Atoms of the same element are identical 3. Atoms of different elements are unique 4. Atoms are not created or destroyed but they combine or break apart in whole number ratios
Describe the Cathode Ray Experiment. Who performed this experiment? This experiment was performed by JJ Thomson. It consisted of a device that created an electric field. A green ray could be seen going through the electric field from the cathode. Ray was called cathode ray.
What conclusions were drawn from the cathode ray experiment? Cathode rays are negatively charged matter. Rays can be bent by magnetic field. Mass to charge ration is m over e. There is a subatomic particle with a low mass and negative charge that is common to all elements (electron).
Describe the Gold Foil Experiment. Who performed this experiment? Rutherford performed the gold foil experiment. It consisted of an alpha particle beam shooting at a piece of gold foil. Surrounding the gold foil was many screens painted with a flourescent coating making them able to detect radiation.
What happened in the Gold Foil Experiment? What conclusions were drawn? The majority of particles went through the foil, but some bounced back or deflected. Concluded that atoms are mostly empty space. Atoms have a small, massive, positively charged object at their center.
Why gold foil? Why alpha particles? Gold foil is very malleable and its atoms have large nuclei. Beta rays scattered too much.
Who created the mass spectrometer? What was it? JJ Thomson created the mass spectrometer. It separates atoms by affecting them based on mass. Thomson discovered elements with different masses (isotopes).
Who discovered the atomic number? Moseley, a student of Rutherford.
Describe the Oil Drop Experiment. Who performed this experiment? Millikan performed the Oil Drop Experiment. He sprayed oil into an electric field. He then shot x-rays at the drops. Ions from the air stuck. Some oil droplets suspended mid-air because of the combination of the ions and the electric field.
What conclusion was drawn from the Oil Drop Experiment? Millikan was able to determine the mass of a single electron.
What is alpha radiation? He +2
What is gamma radiation? energy
What is beta radiation? e-
What is the most important idea that Democritus proposed? IMPORTANT: Matter is discontinuous. Atoms are the smallest peice of matter that retains the properties of matter, and if you cut it, those properties disapear.
Created by: 552603522



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