studCh. 3 - Chemistry Atoms First Second Edition Julia...

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1 1 Chemistry: Atoms First Second Edition Julia Burdge & Jason Overby Chapter 3 Quantum Theory and the Electronic Structure of Atoms
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2 The Nature of Light The speed of light ( c ) through a vacuum is a constant: c = 2.99792458×10 8 m/s Normally rounded to, c = 3.00×10 8 m/s. Speed of light, frequency and wavelength are related: λ is expressed in meters v is expressed in reciprocal seconds (s −1 ) s -1 is also known as hertz (Hz)
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3 Properties of Waves All forms of electromagnetic radiation travel in waves. Waves are characterized by: Wavelength ( λ; lambda ) – the distance between identical points on successive waves Frequency ( ν; nu) – the number of waves that pass through a particular point in 1 second. Amplitude – the vertical distance from the midline of a wave to the top of the peak or the bottom of the trough.
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A photon of light has a frequency of 3.26 x10 15 hertz. What is its wavelength? The speed of light is 3.00 x 10 8 m/s. ? 4
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7.5 Electromagnetic Spectrum γ-rays X-rays UV IR Microwave Radiowave FM AM Longwave radio Frequency (Hz) 10 24 10 22 10 20 10 18 10 16 10 14 10 12 10 10 10 8 10 6 10 4 10 2 10 0 10 -16 10 -14 10 -12 10 -10 10 -8 10 -6 10 -4 10 -2 10 0 10 2 10 4 10 6 10 8 Wavelength (m) 400 450 500 550 600 650 700 Wavelength (nm) Bacterial Animal Thickness Width Dog cell cell of a CD of a CD Atom Virus Visible light is a very small portion of the entire spectrum Visible light is a very small portion of the entire spectrum Energy increases from the radio wave end (low  long λ) to the gamma ray end (high , short λ) Energy increases from the radio wave end (low  long λ) to the gamma ray end (high , short λ)
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6 The energy E of a single quantum of energy is h is called Planck’s constant: 6.63×10 −34 J∙s The idea that energy is quantized rather than continuous is like walking up a staircase or playing the piano You cannot step or play anywhere ( continuous ), you can only step on a stair or play on a key ( quantized ) . Quantization of Energy
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Determine the energy of a photon that has a frequency of 5.23 x10 14 Hz. Given: h = 6.63 x 10 -34 J s. ? 7
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Determine the energy of a photon that has a wavelength of 488 nm. The speed of light is 3.00 x 10 8 m/s and h = 6.63 x 10 -34 J s. ? 8
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Which transition would involve the emission of a photon with the longest wavelength? ____________ E 3 ____________ E 2 ____________ E 1 ?
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Which energy corresponds to a photon with the shortest wavelength? ?
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7.11 The square of the function, 2 , gives the probability of finding an e - at a point. It is always positive. Quantum Model of the Atom Schrödinger’s theory assumed that e - ’s acted as waves and not particles. Solutions of the wave equation are energies and mathematical functions. A ground-state probability map for the H-atom showing 2 for each point in space. Bigger value = darker shade. The functions are called wave functions , .
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