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UMD ENEE 313 - Quiz #3

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ENEE 313, Spr. ’09 Quiz III - Feb 23, 20091. How many valence shell electrons do the following atoms have?(a) (2 pts.) Phosphorus, P: 1s22s22p63s23p3.5 valence shell electrons in shell n=3.(b) (2 pts.) Calcium, Ca: 1s22s22p63s23p64s22 valence shell electroncs in shell n=4.(c) (3 pts.) Fluorine, F: Atomic number 9 (write the electronic configuration first.)1s22s22p5: 7 valence shell electrons in shell n=2.(d) (3 pts.) Boron, B: Atomic number 5 (write the electronic configuration first.)1s22s22p1: 3 valence shell electrons in shell n=2.2. (6 pts.) Consider three fictional materials, A, B and C. At T=0 K,• The valence band of material A is full. The minimum of the valence band is at 1 eV, and themaximum is at 3 e V. The next band of A is empty. The minimum of this band is at 9 eV, themaximum at 14 eV.• The valence band of material B is full. The minimum of the valence band is at 1 eV, themaximum is at 3 eV. The next band of B is empty. The minimum of this band is at 4 eV, themaximum at 6 eV.• The valence band of material C is full. The minimum of the valence band is at 2 eV, and themaximum is at 4 eV. The next band of C is empty. The minimum of this band is at 3 eV, themaximum at 5 eV.If all three materials are examined at the same new temperature T>0 K, which of these materials isthe best conductor? Which is the worst? Briefly explain your answer.At the same temperature, A will have the lowest conductivity since its bandgap is the largest,and C will have the highest conductivity (best conductor) since it does not have a bandgap,but effectively a half-empty band, with electrons at the high levels of the ”valence” band havemany states available to them at the same energy in the overlapping ”conduction” band.Turn over for the last question.13. Remember that the quantum numbers n, m and l are the separation constants in the solution ofthe time-independent Schr¨odinger Wave Equation. Each separation constant comes up during thesolution of the equation for one of the three coordinate dependencies. m is related to the quantizationof the z-component of the angular momentum; l to that of the total angular momentum, and n tothat of the energy.(a) (2 pt.) Match each quantum number to the relevant coordinate.The magnetic quantum number, m rThe orbital quantum number, l φThe principal quantum number, n θm → φ, l → θ, n → r(b) (2 pt.) The orbital quantum number l values 0, 1 and 2 correspond to the s, p and d orbitalsrespectively. Sketch the general shape for the s and p


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UMD ENEE 313 - Quiz #3

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