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Arrangement of Electrons in Atoms

Arrangement of Electrons in Atoms. The Development of a New Atomic Model - 4.1. The Old Atomic Model. Problem with Rutherford model – no explanation of where e-s are New info about light led to new model of the atom Before 1900 scientists thought light traveled like a wave .

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Arrangement of Electrons in Atoms

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  1. Arrangement of Electrons in Atoms The Development of a New Atomic Model - 4.1

  2. The Old Atomic Model • Problem with Rutherford model – no explanation of where e-s are • New info about light led to new model of the atom • Before 1900 scientists thought light traveled like a wave. • We know now that light behaves like a wave and like a particle

  3. The Wave Description • Called the dual wave-particle nature of light! • Electromagnetic Radiation - form of E that exhibits wavelike behavior as it travels thruspace • Electromagnetic Spectrum - all of the formsof electromagnetic radiation (visible light, x-rays, uv and infrared light, micro and radio waves)

  4. The Wave Description • All types of emag rad. move at 3.00 x 108m/sin a vacuum. (slightly slower thru matter) • This is the speed of light

  5. The Electromagnetic Spectrum

  6. Wavelength and Frequency • Wavelength - λthe distance between corresponding ptson adjacent waves • Frequency - νthe number of waves that pass agivenpoint in a specific time, usually 1 second • Frequency is expressed in Hertz (Hz)

  7. The Relationship B/T Freq. and Wavelength • c = λν • The speed of light = wavelength times frequency • The wavelength of red light is 7.6 x 10-7 m, calculate the frequency. • F = speed      =  2.998 x 108 m/swavelength            7.6 x 10-7 m • Frequency = 3.9 x 1014Hz

  8. The Photo-electric Effect • The emission of e-s from a metal when light shines on the metal • Light had to be a certain freq. to emit e-s

  9. The Particle Description of Light • Planck proposed idea of quanta (E packets) • Quantum of energy - the minimum quantity of E that can be lost or gained by an atom

  10. The Particle Description of Light • E = hν • Where E is the energy in joules of a quantum of radiation • υis the frequency in s-1 • h is Planck's constant of 6.626 x 10-34 J *  s

  11. Einstein and the dual particle-wave nature • Ein. supported Planck by proposing the duality of light as particle and wave • Ein. proposed particles of light carry a quantum of E called photons (0 mass)

  12. Einstein and the dual particle-wave nature • The E of a photon depends on the υof rad. • E absorbed in whole # of photons • Different metals need diff. υto remove an e-

  13. The Line Emission Spectrum LES = the result from a narrow beam of the emitted light that is shined through a prism when it separated into colors of the visible spectrum The Continuous Spectrum

  14. The H atom and the LES Electric current passed thru a gas at a low pressure

  15. E Levels • Ground state - the lowest E level of an atom (very stable level) • Excited state - a state in which an atom has a higher potential E than it has in its ground state

  16. E Levels • When an e- falls from the excited state, a photon is given off - the E of the photon is = to the E difference • H only emits certain freq. so e- exists in specific E levels

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