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11.2 – ATOMIC EMISSION SPECTRA (C – LEVEL)

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CHEMISTS THINK THEY’RE COOL…

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OBJECTIVES WWBAT… Explain atomic emission spectra Determine the possible energies of photons emitted from an atom

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PRISMS AND RAINBOWS

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LET’S TAKE A LOOK AT COLORED FLAMES…

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ATOMIC EMISSION SPECTRA Fingerprint of an element Occurs when an element is excited and allowed to return to its ground state

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FORMATION OF ATOMIC EMISSION SPECTRA

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As an electron moves up energy levels, it increases its energy Energies closest to the nucleus have large, negative energies (remember, PE elec = kqq/d) Atoms, theoretically, have an infinite number of energy levels, with n = infinity having an energy of zero.

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DETERMINING THE WAVELENGTH OR FREQUENCY E i – E f = energy of photon (hƒ) *NOTE: in advanced texts, frequency is denoted by the Greek letter nu, which looks a lot like a v. The Texas Eduation Agency has decided frequency is denoted by the fancy f, whose name is unbeknownst to me. *Additional fun fact: in advanced texts, potential energy is not denoted by “PE,” but by the letter U. The more you know…

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EXAMPLE The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom? A)48.36 eV B)40.8 eV C)21.6 eV D)7.36 eV E)3.20 eV

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EXAMPLE The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom? A)48.36 eV B)40.8 eV C)21.6 eV D)7.36 eV E)3.20 eV Transition to…n = infinityn = 4n = 3n = 2 n = 4 n = 3 n = 2 n = 1

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EXAMPLE The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom? A)48.36 eV B)40.8 eV C)21.6 eV D)7.36 eV E)3.20 eV Transition…n = infinityn = 4n = 3n = 2 n = 44.2 eV n = 36.04 eV1.84 eV n = 213.6 eV9.4 eV7.36 eV n = 154.4 eV50.2 eV48.36 eV40.8 eV

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EXAMPLE The first four energy levels of an atom are listed above. Assume n = 4 has an energy of -4.20 eV, and the highest energy level (n = infinity) is 0 eV. Which of the following energies is not possible for a photon emitted from this atom? A)48.36 eV B)40.8 eV C)21.6 eV D)7.36 eV E)3.20 eV Transition…n = infinityn = 4n = 3n = 2 n = 44.2 eV n = 36.04 eV1.84 eV n = 213.6 eV9.4 eV7.36 eV n = 154.4 eV50.2 eV48.36 eV40.8 eV

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CHECK YOURSELF The following diagram illustrates the energy levels for an atom. A photon of which energy would not be able to be emitted from this atom? A) 13.6 eV B) 12.1 eV C) 10.2 eV D) 6.45 eV E) 1.12 eV

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CHECK YOURSELF The following diagram illustrates the energy levels for an atom. A photon of which energy would not be able to be emitted from this atom? A) 13.6 eV B) 12.1 eV C) 10.2 eV D) 6.45 eV E) 1.12 eV

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OBJECTIVES WWBAT… Explain atomic emission spectra Determine the possible energies of photons emitted from an atom

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