Chem 1211 1st Edition Lecture 17 Outline of Last Lecture I Waves II Electromagnetic Radiation III Photoelectric Effect Outline of Current Lecture I Atomic Spectra II Quantization Steps III Wave Nature of Electrons Current Lecture I Atomic Spectra a ConcepTest Which electronic transition would you expect to have the smallest energy gap i n1 1 to n2 2 ii n1 2 to n2 3 iii n1 1 to n2 3 iv n1 2 to n2 4 v n1 6 to n2 7 1 ANSWER V N1 6 to N2 7 2 REASONING The gaps decrease as N increases b Rydberg Equation c 1 wavelength R 1 n12 1 n22 i R 1 097 x 107 m 1 ii n1 n2 d ConcepTest Which electronic transition of hydrogen would you expect to occur in the visible range of electromagnetic radiation i n1 1 to n2 2 ii n1 1 to n2 3 These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute II III iii n1 2 to n2 3 iv n1 4 to n2 5 v depends on the value of Planck s constant 1 ANSWER iii n1 2 to n2 3 2 REASONING Anything that starts with 1 is too energetic anything that starts with 3 is not energetic enough Use a graph or calculate by hand Quantization Steps a Electrons particles waves b deBroglie wavelength i w h mv 1 m mass 2 v velocity c ConcepTest Usain Bold may be the fastest human with a speed of 23 mph 10 3 m s He weighs 94 kg What is his deBroglie wavelength at that speed h 6 626 x 10 34 Js J kgm2s 2 i ANSWER 6 84 x 10 37m ii REASONING Use the equation w h mv Wave Nature of Electrons a Louis de Broglie 1925 i w h mv b Many diagrams show a Bohr model in which the electrons orbit the nucleus in a perfect circle THIS IS NOT RIGHT If this were true the electrons would fall into the nucleus when they decay leading to the end of all matter c Quantum mechanics orbitals probability i You can find the probability of where an electron is but you can never find out for sure When you try to experiment you change the orbital enough that the position of the electron changes as well d Quantum Numbers Review i Principal quantum number n 1 2 3 4 Shells rows in periodic table ii Angular momentum quantum number I 0 1 2 n 1 OR l s p d f g h n 1 defines shapes iii Magnetic quantum number mI I I 1 0 I 1 I 1 I 0 s orbital mI 0 only 1 value 2 I 1 p orbitals mI 1 0 1 three p orbitals x y z 3 I 2 d orbitals mI 2 1 0 1 2 five shapes directions 4 I 3 f orbitals mI 3 2 1 0 1 2 3 7 shapes directions iv Spin quantum number ms 1 2 or 1 2 1 Means that there are no more than 2 electrons per orbital 2 Spin parallel antiparallel v ConcepTest What are the values of n I and ml for a 4s orbital 1 0 4 1 2 3 4 5 4 0 1 4 0 0 Depends on the spin Requires more info a ANSWER 3 4 0 0 b REASONING For a 4s orbital the n 4 and the only options for I and mI are 0 vi Atomic Orbital Shapes 1 s sphere 2 p dumbbell 3 d multiple 4 f complex vii Electron Spin and Electron Occupancy 1 Spins describe direction of electon s magnetic field a Simple description spin up or spin down 2 Paramagnetic atoms unpaired elctrons a Have net magnetic ions 3 Paramagnetism net field in external magnetic field 4 Diamagnetism no net magnetic field 5 Ferromagnetism permanent magnetic field
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