8.Atomic_Structure

8.Atomic_Structure - ATOMIC STRUCTURE Topics you must know:...

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ATOMIC STRUCTURE Topics you must know: 1. Calculations of wavelength and frequency 2. Wave/Particle Duality of Light 3. Calculations of atomic energy levels for one-electron atoms 4. The Quantum nature of electron orbitals 5. Orbital and subshell energy diagrams 6. Electron configurations Problems Chapter 9 (All) 25,26,31,34,45,49,69,83,85,87 Chapter 10 (Omit Electron Affinity) 33,41,43,46
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Atoms H -Hydrogen Atom smallest and simplest atom composed of one proton and one electron Plum-pudding atomic model (Fig 2-9) Fig 2-11. Scattering of particles by metal foil (1919)
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Fig. 2-13 The nuclear atom - the He atom
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. . nucleus electron Chemical properties mainly due to the electrons HH O 104° 0.97Å Molecular Shape…bent or angular Bonds Need to know how molecules hang together, but before we can do this we need to understand how electrons in atoms behave before we start thinking about molecules
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Electromagnetic Radiation Fig 9-3 The Electromagnetic Spectrum
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Figure 9-8 Sources for light emission hydrogen helium lithium sodium potassium Figure 9.9 The atomic, or line, spectrum of helium
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line spectra of several atoms Fig 9-1 Travelling wave in a rope
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Wavelength = Distance between the crests of the wave Frequency = the number of crests that pass a given point per second (s -1 or Hz (Hertz)) Connection between the two wavelength x frequency =velocity =speed of light x = c c = 3.00 x 10 8 m s -1 Q. What is the wavelength of the radiowaves emitted by CITR radio @ 101.9 MHz = c and Hz = s -1 MHz = 10 6 Hz 101.9 x 10 6 s -1 = c = 3.00 x 10 8 m s -1 = 2.94 m
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Light as Energy 1888, Heindrich Hertz discovered that when light strikes the surface of certain metals, electrons are ejected. Fig 9-12 The photoelectric effect • electrons are ejected only after a threshold frequency of the light is exceeded • the number of electrons ejected depends upon the intensity of the light • but the kinetic energies of the ejected electrons depends upon the frequency of the light
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1905: Einstein explains the photoelectric effect: • light does not behave like MATTER waves eg. at sea the energy of the waves are proportional to the amplitude of the wave • the energy of light is proportional to the frequency of the light New way of looking at light. • Light is composed of small packets of energy called photons • The energy of an individual photon is given by PLANCK’S equation for electromagnetic radiation: E = ν • h = Planck’s constant = 6.626 x 10 -34 J(oules) , “nu” or “n”. ...frequency ...upsilon “u”. .not frequency
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E = ν = c Calculate the energy in Joules of one photon of yellow light, = 580.5 nm and of one mole of these photons = 6.626 x 10 -34 J s photon -1 c = 3.00 x 10 8 m s -1 = 6.626 x 10 -34 J s photon -1 x 3.00 x 10 8 m s -1 580.5 nm/10 9 nm m -1 = 3.42 x 10 -19 J photon -1 x 6.022 x 10 23 photon mol -1 = 206 x 10 3 J mol -1 Classical Physics: Negatively charged electrons should be pulled into the positively charged nucleus unless they have momentum (motion) much like the planets around the sun.
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8.Atomic_Structure - ATOMIC STRUCTURE Topics you must know:...

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