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Warm Up

Warm Up. What is the wavelength defined as? You are given the wavelength of a particle as being 6.3 x 10 -5 m. What is the frequency of the particle ? You are given the frequency of a particle as 7.43 x 10 14 Hz. What is the wavelength? HINT: Speed of light = 3.00 x 10 8 m/s. Chemistry.

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Warm Up

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  1. Warm Up • What is the wavelength defined as? • You are given the wavelength of a particle as being 6.3 x 10 -5 m. What is the frequency of the particle? • You are given the frequency of a particle as 7.43 x 1014 Hz. What is the wavelength? • HINT: Speed of light = 3.00 x 108 m/s

  2. Chemistry Unit Three, Day Two Kimrey 18 September 2012

  3. Electromagnetic Spectrum • Shows the different types of radiation – different wavelengths.

  4. Radio Waves • Radio waves are electromagnetic waves with the longest wavelengths (longer than 1mm) • They are used in communications, radar, microwaves, and MRIs

  5. Microwaves • Microwaves are radio waves with wavelengths less than 30 cm but longer than 1mm • Cell phones and satellites use microwaves • Microwaves in microwave ovens cause water molecules to rotate, heating your food

  6. Infrared Waves • Infrared waves have wavelengths between 1mm and 750 billionths of a meter • Thermal energy travels in infrared waves • Remote controls and • CD-ROM drives also use • infrared waves

  7. Visible Light • The visible spectrum is the light we can see • In order from largest wavelength to smallest: Red, Orange, Yellow, Green, Blue, Indigo, Violet (Roy G Biv) • The color you see is the color that is reflected. • White is all colors, black is no color. • The longer the wavelength, the less penetrating (including less dangerous to cells)

  8. Visible Light (ROYGBIV)

  9. Ultraviolet Waves • Ultraviolet, or UV waves, have wavelengths of 400 billionths to 10 billionths of a meter • UV waves can cause skin damage such as sunburn, wrinkling, and cancer

  10. Ultraviolet Light • UV light enables your body to make vitamin D • UV waves can kill bacteria by damaging its DNA

  11. X-Rays • X-rays have wavelengths between ten billionths of a meter and ten trillionths of a meter • X rays are commonly used by doctors and dentists

  12. Gamma Rays • Gamma waves have wavelengths shorter than 10 trillionths of a meter • Gamma rays are produced by radioactive decay or other subatomic processes

  13. The Bohr Model • Created by Niels Bohr in 1913. • Related the energy of an electron to the orbital it would occupy. • Similar to the model of the solar system with the nucleus as the sun.

  14. 1stshell can hold 2 electrons. • 2nd can hold 8. • 3rd can hold 18 • 4th can hold 32

  15. Making Bohr Models • Step One: Write the number of protons and neutrons in the nucleus. • Step Two: Add electrons in their appropriate orbitals until you have reached the correct number of electrons.

  16. Example • Draw a Bohr model for Mg-24.

  17. You Try • Draw a Bohr model for the following: • Nitrogen-14 • Aluminum -27 • Sodium-23+1

  18. Conclusions from the Bohr Model • Electrons are both Particles AND waves. • We cannot know for certain where an electron is. • We cannot know for certain how fast an electron is moving. • The more we know about the location of an electron the less we know about its’ movement and vice versa.

  19. Bohr Model and Light • Bohr went a step further as well, he determined that each orbital corresponded to a certain energy level. • As electrons become excited they can “jump” to a higher energy level. • When these electrons return to their ground state (normal energy level) they emit the difference in energy levels. • NOTE!!! Electrons can ONLY exist at a specific orbital NOT between orbitals.

  20. Reading the Bohr Model

  21. Example • What is the wavelength of light emitted when an electron goes energy level 4 to energy level 1? • (n=4  n=1) • 97 nm

  22. You Try • What is the wavelength of light emitted when an electron goes from n= 3 to n = 2? • What type of light would this be classified as? • A photon with a wavelength of 656 nm is emitted from a hydrogen atom. What energy state did this electron start in and end in?

  23. Bohr Model for H Atom

  24. Example Problems • What type of light has a wavelength of 1 x 10-11 m?  • What type of light is released when an electron jumps from = 4 to n = 1 in a Hydrogen atom? • What type of light has a wavelength of 6.3 x 10 -7m? • Is light energy released or absorbed in the following jumps of an electron in a Hydrogen atom? • n=1 to n = 3 • n = 2 to n = 5 • n = 6 to n = 3 • n = 2 to n = 3 • Rank the following types of light in increasing energy: X – ray, green light, microwaves, violet light.

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