# AtomII.ppt

30 de May de 2023
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### AtomII.ppt

• 1. Atomic Structure II (Ch.5) Introduction: Wave-Particle Nature of Light Discoveries about the nature of light led to greater understanding of the properties of electrons and atomic structure.
• 2. 1800’s: Electrons were thought of as particles; light was thought of as waves. Experimental observations can support both these theories. Early 1900’s: New experiments showed that electrons have some wave-like properties and light has some particle-like properties. These discoveries led to the idea that both electrons and light have a dual wave-particle nature. (This was the beginning of quantum physics.)
• 3. I. Light is a form of electromagnetic radiation. A. electromagnetic radiation (EMR)- energy that has wave characteristics as it travels through space.
• 4. 1. Visible light is one form of electromagnetic radiation; others include x-rays, ultraviolet light, infrared light, TV and radio waves. 2. Electromagnetic spectrum – consists of all the forms of EMR arranged in order by wavelength. 3. All types of electromagnetic radiation travel at a speed of 3.00 x 108 m/s. This is called the speed of light (c).
• 6. Waves Waves transfer energy from one place to another B. Electromagnetic radiation has the following wave characteristics:
• 7. 1. Wavelength,  (lambda) = distance between successive points 10 m 2m
• 8. 2. Frequency,  (nu) = the number of waves that pass a given point per unit of time; Cycles per second t=0 t=5 t=0 t=5
• 9. Units for Frequency • 1/s • s-1 • hertz, Hz FM Radio stations are identified by their frequency in MHz. ; AM Radio stations are identified by their frequency in kHz.
• 10. 3. Wave Velocity • Velocity of a wave (m/s) = wavelength (m) x frequency (1/s) • c =  • 3.00x108 m/s = 
• 11. Because all electromagnetic waves travel at the speed of light, wavelength is determined by frequency: Low frequency = long wavelengths High frequency = short wavelengths Wavelength and frequency are inversely proportional.
• 12. 1. The yellow light given off by a sodium vapor light has a wavelength of 589 nm. What is the lights frequency? 2. A laser used to fuse detached retinas has radiation with a frequency of 4.7 x 1014 Hz. What is its wavelength in nm?
• 13. 3. Calculate the wavelength (in nm) of a microwave that has the frequency of 3.25 x 1010 Hz. 4. What is the frequency of blue light that has a wavelength of 475 nm? 9.23 x 106 nm 6.31 x 1014 Hz
• 14. 1. An x-ray has a frequency of 2.5 x 1018 Hz. What is the wavelength of the x-ray? 2. A red light has a wavelength of 725 nm. What is the frequency of the red light?
• 15. C. Prisms A prism can be used to “spread out” the wavelengths of light.
• 16. Continuous spectrum – a spectrum in which all the wavelengths within a given range are included. A rainbow would be an example of a continuous spectrum of visible light.
• 18. Light shows the wave property of Interference. (Physics 2000 – Interference Experiments) D.
• 19. II. Light as a Particle two properties of light could not be explained in terms of waves: A) emission of light by hot objects; B) the photoelectric effect.
• 20. A. (1900) Max Planck says energy can only be released or absorbed by atoms in "packets of energy" called quanta. The energy of a quantum (E) is given by the equation: E = h  = frequency; h = Planck's constant: 6.63 x 10-34 Js EX: Calculate the energy of a quantum of radiation whose frequency is 3.0 x 1011 Hz.
• 21. • Higher-frequency electromagnetic waves have higher energy than lower-frequency electromagnetic waves • All forms of electromagnetic energy interact with matter, and the ability of these different waves to penetrate matter is a measure of the energy of the waves
• 22. Photoelectric Effect Animation B. Photoelectric Effect - the phenomena whereby a metal will emit electrons if light with a certain minimum frequency is shined on it.
• 23. (1905) Einstein explains photoelectric effect by saying that light consists of quanta. Only if the light has a high enough frequency will the quanta have enough energy to dislodge an electron. Einstein called these quanta or "particles" of light photons. Light (and all electromagnetic radiation) has both wave-like and particle like properties.
• 24. EX Problem 1: A purple light has a frequency of 7.5 x 1014 Hz. What is the energy of a photon of purple light? EX2: A green light has a wavelength of 500. nm. Calculate the energy of a photon of green light. 5.0 x 10-19 J 3.98 x 10-19 J
• 25. •A blue light has a frequency of 6.7 x 1014 Hz. Calculate the energy of a photon of blue light. •Radio signals from station WIP have a frequency of 6.1 x 105 s-1. Calculate the energy of a photon of this radio signal. •A yellow light has a wavelength of 575 nm. Calculate the energy of a photon of this light. 4.4 x 10-19 J 4.0 x 10-28 J 3.46 x 10-19 J
• 26. III. Line Spectra (bright-line spectra, atomic emission spectra) 1. Line Spectra ( or bright-line spectra) – these lines of color are produced when the light from an element is passed through a prism. 2. Each element produces a characteristic set of lines called the line spectrum of the element. Elements can be identified by their line spectrum. 3. Each line in a line spectrum represents a particular wavelength and frequency of light given off. You can calculate the energy of the photons of light using E=h 4. Bohr used the line spectrum of hydrogen to devise his model of the atom.
• 27. III. Line Spectra 1. Physics 2000 – Quantum Atom - Line Spectra 2. Line Spectra Animation
• 29. Quantum Model of Atom A. (1924) Louis de Broglie says if light has a dual wave-particle nature, then matter (electrons) could also have a dual wave-particle nature. I. Quantum Mechanics
• 30. Electron Interference Animation(Web) Drive Experiments showed that electrons display the wave properties of diffraction and interference.
• 31. B. Heisenberg Uncertainty Principle It is impossible to know exactly both the location and velocity of an electron at the same time.
• 32. C. Schrodinger Wave Equation Describes the probability of where an electron can be found. Schrodinger’s equation works for all atoms. D. Quantum theory – describes mathematically the wave properties of electrons. In the quantum model of the atom, electrons are found in orbitals, not specific orbits.

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