The theory of atom
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Rutherford discovered alpha particles emitted from uranium in 1899. Alpha particles are high-speed particles composed of two protons and two neutrons, identical to a helium nucleus but without electrons. Rutherford found uranium emitted at least two types of radiation, which he called alpha and beta particles, and determined through experiments shielding the uranium with aluminum sheets of varying thickness that alpha particles are stopped by just a few inches of air due to being a high-energy nuclear particle.
The theory of atom
- 1. Rutherford’s Theory Albert C. (x-10) (1) Julius C. (x-10) (11) Nicholas S. W. (x-10) (17) Sinclair K. (x-10) (19)
- 2. background • Born in brightwater, New Zealand 30 August 1871 • Son of James Rutherford and Martha Thompson • Student of J.J. Thomson • Take school in new zealand (M.A.)(master of arts), canada (B.A.)(bachelor of arts) and england (Professor of Physics)
- 3. His research • Alpha “rays” / particles • Theory of protons • Detector for electromagnetic waves
- 4. In 1899, Rutherford had discovered alpha "rays" from uranium. Now, today we know they are not rays, they are particles; alpha is a nucleus of helium.
- 5. What are alpha rays / particles? • High speed particles • Made up of two protons and two neutrons • Is a nucleus, same as the nucleus of a common atom of helium • Don’t have electrons around it • Type of ionizing radiation • will loose all their energy in just a couple inches of travel in air
- 8. A uniform layer of powered uranium compound was spread on plate A and the rays allowed to ionize the gas between plates A and B. The amount of ionization is measured by the "saturation current" received at B when the potential difference between A and B is great enough to pull all the ions to the plates before they are able to recombine. Rutherford then proceeded to cover the uranium with aluminum sheets of various thicknesses and measure the current, using the electrometer. Rutherford was in the process of checking to see if this was true or not, because Becquerel had also made other claims about uranium radiation which turned out to be incorrect. Now, what Rutherford did find was that there were at least two different "rays" being emitted by the uranium and he called them α and β.
- 9. What are alpha rays? Alpha "rays" are actually high speed particles. An alpha particles is made up of two protons and two nneutrons, all held together by the same strong nuclear force that binds the nucleus of any atom. In fact, an alpha particle really is a nucleus - it's the same as the nucleus of a common atom of helium - but it doesn't have any electrons around it, and it's traveling very fast. Alpha particles are a type of ionizing radiation. but Alpha particles will loose all their energy in just a couple inches of travel in air. Once an alpha particle is stopped, it grabs the first two free electrons it can find, and becomes a plain old atom of helium.