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Atomic Structure

Atomic Structure. The Electron and Light. Atoms and Light. About 100 years ago some scientists noticed that certain elements emitted different colors of visible light when heated in a flame . More research helped them connect this light to the arrangement of each element’s electrons.

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Atomic Structure

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  1. Atomic Structure The Electron and Light

  2. Atoms and Light About 100 years ago some scientists noticed that certain elements emitted different colors of visible light when heated in a flame. More research helped them connect this light to the arrangement of each element’s electrons.

  3. LIGHT • To understand the structure of the atom we need to learn about light and how it can act like a wave and a particle at the same time . • Simply stated, light is nature's way of transferring energy through space , light is energy.

  4. Light can behave like a wave wave pattern

  5. Light as Waves –The Electromagnetic Spectrum Low frequency Long wavelength Low energy High frequency Short wavelength High energy 400nm 700nm Visible light ROYGBIV

  6. Electromagnetic radiation is energy that behaves like a wave as it moves through space. • Radio and TV stations transmit using low energy radio waves that range from millimeters to kilometers in length • Microwaves not only cook; they transmit cell phone signals ; they are measured in centimeters • X rays are about 10 nanometers long and can travel through your muscle and skin • Gamma rays are very powerful; they can cause cancer and sometimes cure it. They are about a picometer long Do you see any pattern here?

  7. Light and Quantized Energy Radiation having lower energy, such as ultraviolet, visible, infrared light, radio and microwaves, also has longer wavelengths and lower frequency. Higher energy electromagnetic energy (radiation) such as x rays and gamma rays has shorter wavelengths and higher frequency. . http://www.colorado.edu/physics/2000/quantumzone/frequency.html

  8. Wavelength (λ)crest to crest(A –F);trough to trough (D – I) Amplitude: origin to crest or trough Frequency (ν) how many λ pass per second Speed(c) all emr waves travel at speed of light c= 3 x 108 m/s Describing Waves

  9. Wavelengths, frequency All electromagnetic radiation (emr) travels at 3 x 108 m/s. But different emr waves can have different wavelengths and frequencies. Longer wavelength lower frequency, Shorter wavelength higher frequency Inversely related. λ≈1/νν≈1/λ What is the constant that relates them?

  10. Wavelengths. Frequency The constant that relates them is cthe speed of all light waves, all electromagnetic radiation. c = λν The speed of light = wavelength x frequency This equation can be used to calculate the wavelength or frequency of any wave of electromagnetic radiation.

  11. Light and Quantized Energy A wave of visible light has a frequency of 7.5 x 10 14 wavelengths /second. Frequency units: wavelengths per second is also called Hertz or 1/s or s-1 What is the wavelength? 3x108m/s = λ 7.5 x 10 14Hzλ = 4 x 10-7m

  12. Light behaves like a particle photoelectric effect Photoelectric effect colorado

  13. Absorption at the quantum level happens when an individual photon has the exact energy that corresponds to an energy gap between two possible energy states. The type of energy gap corresponds directly to the frequency of the photon Light is absorbed by electrons in “chunks” or particles. A particle of light is a photon. Photons Photon absorption and emission

  14. Photons Light is seen when the electron emits the photon of light. Since different photons have different energy and frequencies, it is possible to see different colors. Some photons are too high energy to be seen – UV and some are too low energy to be seen – infrared.

  15. Light and Quantized Energy E quantum = hν E = energy of the photon H = Planck’s constant ν = frequency • http://www.colorado.edu/physics/2000/quantumzone/bohr.html

  16. Light and Quantized Energy A photon of visible light has a frequency of 4.3 x 10 14 wavelengths /second. What is the energy of this photon? E = (6.626 x 10 -34 J•s)(4.3 x 10 14 s-1) = 28.5 x 10 -20 Joules Joules are just an energy unit – like calories = 2.85 x 10 -19 J

  17. Putting it all together Atomic emission spectra – each element has a unique spectrum of colors that it produces as the electrons absorb energy. A spectrum is like the element’s “fingerprint”. Spectra

  18. Not all spectra are visible; some are too high frequency; some are too low frequency Visible Hydrogen spectrum

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