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Chapter 5.3 Light, Wavelength and the Atomic Spectrum

Explore the properties of light, including its wavelength and frequency, and learn how elements emit light to create atomic emission spectra.

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Chapter 5.3 Light, Wavelength and the Atomic Spectrum

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  1. http://wild-turkey.mit.edu/Chemicool/www.acs.org Chapter 5.3Light, Wavelength and the Atomic Spectrum http://www.anachem.umu.se/cgi-bin/pointer.exe?PeriodicTables

  2. I. Light When a sample absorbs visible light the color we see is the sum of the remaining colors that are __________ or ___________ by the object. reflected transmitted light An opaque object reflects _________ and a clear object ________ light. transmits If an object absorbs all wavelengths of visible light and no color reaches our eyes, the object appears ______________. Black

  3. I. Light When sunlight (white light) passes through a prism, the different wavelengths of light separate into a spectrum of colors, which are? ROYGBIV Example: Rainbow

  4. WHITE LIGHT

  5. Electromagnetic spectrum • Consists of radiation over a broad band of wavelengths and frequencies. • What are some different types of radiation? Ultraviolet, infrared, X-rays, gamma rays … • Can we see these different types of radiation? No, Why?

  6. Electromagnetic spectrum cont… What is one type of radiation that we do see with our eyes, which is a small part of the electromagnetic spectrum? Visible light Visible light is just one form of electromagnetic radiation.

  7. Electromagnetic Spectrum

  8. The microwave was invented after a researcher walked by a radar tube and a chocolate bar melted in his pocket. Mmmmm… chocolate…. The Microwave Oven

  9. Visible Light Exists at a wavelength of 1 x10-7 m at a frequency of 1 x 1015 Hz on the electromagnetic spectrum. Violet Indigo Blue Green Yellow Orange Red 400 nm 450 nm All of these colors blend together at high frequencies to produce what color of light? 480 nm 500 nm 560 nm 600 nm White light 650-750 nm

  10. Visible Light cont… Which color of light has the longest wavelengthand thelowest frequency? Red Light Which color of light has the shortest wavelength and the highest frequency? Violet light The wavelength and frequency of each color of light is a __________ of that color. quantitative characteristic

  11. Wavelength and Frequency What do we mean when we say the word “light” & how does this relate to wavelength and frequency? waves high Light travels in ______ with either ____ or ___ frequencies at a speed of _____________ (in a vacuum). low 3.00 x 108 m/s c = speed of light = 3.00 x 108 m/s What type of radiation refers only to that part of the electromagnetic spectrum that we can see with the human eye? Visible Light

  12. Definitions: Origin is where each wave cycle begins. Define amplitude. Height of the wave from the origin to the crest (top of wave) Define wavelength. () Symbol  Distance between two crests Define frequency. (ν) # of wave cycles to pass a given point per unit of time.

  13. C = V In a wave: Crest - top of the wave Wavelength Amplitude Origin

  14. As the wavelength of light increases (distance between the crests) what happens to the frequency? ν = c s-1 = /sec λ In a wave cont … decreases Calculating the frequency of a wave: c = λν The SI unit for frequency is: Hertz (Hz) or s-1

  15. ν = c s-1 = /sec λ Calculate the frequency of a wave whose wavelength is 6.0 x 10-5 cm. 6.0 x 10-5 cm 1 m = 6.0 x 10-7 m cm 100 ν= 3.00 x 108 m/s 6.0 x 10-7 m = 5.0 x 1014/s OR = 5.0 x 1014s-1 OR = 5.0 x 1014Hz

  16. Calculate the wavelength of the yellow light emitted by a sodium lamp. The radiation frequency is 5.10 x 1014 s-1. s-1 = /sec c=λν c=λν ν ν λ = 3.00 x 108 m/s = 5.88 x 10-7m 5.10 x 1014/s nm 1 x 109 5.88 x 10-7 m = 588nm m 1

  17. Warm-up - Calculate the wavelength of a photon whose frequency is 6.30 x 1014 s-1. s-1 = /sec c=λν c=λν ν ν λ = 3.00 x 108 m/s = 4.76 x 10-7m 6.30 x 1014/s nm 1 x 109 4.76 x 10-7 m = 476nm m 1

  18. Warm-up - What color of light is produced? = 476nm Blue-Indigo Light Convert the wavelength to cm. m 476 nm cm 1 100 m nm 1 x 109 1 = 4.76x 10-5 cm

  19. Atomic Emission Spectrum

  20. III. Atomic Emission Spectrum How do elements emit light in the gas state? 1 - Elementis vaporized 2 - Pass an electric current through the gas 3 - The electrons in the atom absorb the energy which forces the e- to jump to high energy levels, known as the excited state. 4 - Then, the e- will lose the energy it has just gained and will fall back down to a lower energy level, known as the ground state. 5 - As the e- falls back to the ground state it will give off energy in the form of LIGHT.

  21. III. Atomic Emission Spectrumcont.. Every element emits light! • Passing the emitted light from the element through a prism will give an Atomic Emission Spectrum for that particular element. • These are distinct lines of color that correspond to exact wavelengths. • Each line corresponds to a specific amount of ________ being emitted. energy

  22. Atomic Emission Spectrum (slide) Bands of Color

  23. Light produced from an element can also be separated into distinct wavelengths

  24. III. Atomic Emission Spectrumcont.. How is the atomic emission spectrum useful? Each element gives off a unique set of colors. The colored lines (or Spectral Lines) are a kindof "signature or fingerprint" for the element.

  25. Atomic Emission Spectrumvs. White Light (produced from either sun light or incandescent light bulbs) White light gives a continuousspectrum of colors: the colors are blended together.

  26. Whereas, an Atomic Emission Spectrum (produced from elements) gives distinct bands of color (not all colors of the spectrum are present. • The colors of the lines are dependent upon the specific element. • These lines are called spectral lines. • Each line corresponds to one exact frequency of light emitted by the atom.

  27. The instrument used to see spectral lines is called a spectrometer.

  28. Examples: Na vapor emits a: Argon emits a: Krypton emits a: Xenon emits a: Neon emits a: Orange-Yellow light Lavender light White light Blue light Red-orange light

  29. The quantum of energyabsorbed is equal to h x v Explanation of Atomic Spectrum A single electron in the lowestenergy level __________, can be excited to a higher energy level called the ___________. ground state excited state

  30. E = h v Planck showed mathematically that the amount of energy emitted or absorbed is proportional to the frequency of the radiation. h = Planck’s constant, 6.6262 x 10-34J•s v = frequency, s-1 or /s E = energy, J (joules)

  31. Then, the single electron drops back down from the ____________ to the ______ _____ and the electron releases energy in the form of electromagnetic radiation or _____. E = h v The quantum of energyreleased is also equal to h x v ground excited state state light • The same amount of energy gained is emitted (________) as a photon (______________). released quantum of light

  32. Three groups of lines are possible: Lyman Series Balmer Series Paschen Series e- drops from a high energy level to n=1, ultraviolet light is emitted e- drops from a high energy level to n=2,visible light is emitted (ROYGBIV) e- drops from a high energy level to n=3, infrared light is emitted

  33. Bohr’s Model of the Atom

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