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Rutherford’s gold foil experiment

Rutherford’s gold foil experiment. simulation. Fluorescent screen. Beam of alpha particles. Thin gold foil. Rutherford’s Model of the Atom. 1. The positive charge is concentrated in the nucleus. This is a very small part of the atom.

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Rutherford’s gold foil experiment

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  1. Rutherford’s gold foil experiment simulation Fluorescent screen Beam of alpha particles Thin gold foil

  2. Rutherford’s Model of the Atom 1. The positive charge is concentrated in the nucleus. This is a very small part of the atom. 2. Almost all the mass of the atom is concentrated in the nucleus. 3. Most of the volume of the atom is empty space as 99% of the alpha particles go straight through.

  3. 235 U 92 The atom Mass number – the number of nucleons ( protons + neutrons) Symbol for element Atomic number – the number of protons (this is also the number of electrons)

  4. Unstable nucleus Electromagnetic wave particle Atoms which emit electromagnetic radiation or a particle by the spontaneous transformation of their nucleus are called radioactive.

  5. - Types of radiation • Alpha Particle (α) • Beta Particle (β) • Gamma Ray (γ)

  6. 4 He 2 0 e -1 1 n 0 Alpha particle is a helium nucleus. It has a positive charge. Beta particle is a fast moving electron. It has negative charge Gamma radiation is part of the electromagntic spectrum. No charge. neutron

  7. Radioactive Decay 4 He 2 234 234 234 Th Th Th + 90 90 90 0 0 γ e -1 0 238 U 92 234 234 Pa Th + + 90 91 Has less energy daughter parent

  8. Fission – when a large atom breaks into smaller atoms which have less total mass and so releases energy. Eg. 238 U  234 Th + 4 He + energy. How much energy is released? The mass of 238 U = 3.9508 x 10-25 kg 234 Th = 3.8843 x 10-25 kg 4 He = 6.64 x 10-27 kg 92 90 2 92 90 2 E = mc2 Mass can be changed into energy and vice versa. This is a spontaneous emission of an alpha particle

  9. 42 0 52 94 0 Eg. 3H + 2H  4 He + 1n 1 1 2 0 A stimulated fission, where a neutron makes a large atom unstable and it breaks into smaller atoms releasing energy. Eg. 239 Pu + 1n  137 Te + 100 Mo + 31n Click here Fusion, where two small atoms join to become one larger atom with less mass. ( need very high pressures and temperatures for this to happen ie in the sun)

  10. . . Equivalent dose rate, H, the equivalent dose per unit time, measured in Svh-1 etc H = H ÷ t Activity, A, number of decays per second, measured in Bequerels, Bq. A = N ÷ t Absorbed dose, D, the energy absorbed per unit mass, measured in Grays, Gy. D = E ÷m Radiation weighting factor, wR, a measure of the biological effects of that type of radiation. Equivalent dose, H, the effect that the absorbed dose has on the tissue, measured in Sieverts,SvH = DwR Average equivalent dose = 2mSv

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