9 - CHEMISTRY 121 Problem Set 9 Answer 1. Which of the...

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CHEMISTRY 121 1 Department of Chemistry University of British Columbia Problem Set 9 Answer Atomic Structure II 1. Which of the following orbitals can exist? (a) 3 d (b) 3 f (c) 2 s (d) 5 d (e) 2 d The answers are: A, C and D. l = 0, …, n - 1 n = 2 l = 0, 1 n = 3 l = 0, 1, 2 n = 5 l = 0, 1, 2, 3, 4 subshells: 2s 2p subshells: 3s 3p 3d subshells: 5s 5p 5d 5f 5g Therefore, 2s, 3d, and 5d orbitals can exist because the 2s, 3d, and 5d subshells exist (the quantum numbers corresponding to these subshells are allowed). The 3f and 2d subshells cannot exist because these subshells do not exist (the quantum numbers corresponding to these subshells are not allowed). 2. What is the maximum number of electrons that can be placed in the 4 d z 2 orbital? The answer is: 2 electrons. At most 2 electrons (one "spin-up" and one "spin-down") can occupy an orbital. 3. What is the maximum number of electrons that can be placed in all the 5 f orbitals? The answer is: 14 electrons. There are seven f orbitals in an f subshell. Each orbital can contain a maximum of 2 electrons, therefore the total number of e in all the 4f orbitals is 14. 4. Which of the following sets of quantum numbers ( n , l , m , m s ) are disallowed for an electron in an atom? (a) 4, 2, 0, +1/2 (b) 3, 3, -3, -1/2 (c) 2, 0, +1, +1/2 (d) 4, 3, 0, + 1/2
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CHEMISTRY 121 2 Department of Chemistry University of British Columbia (e) 3, 2, -2, -1 The answers are: B, C and E The rules for the quantum numbers are: n = 1, 2, 3,. ..... l = 0, 1,.…. ., n-1 m l = - , - +1. .. , 0, . .. , -1, m s = -1/2, +1/2. (1) Allowed: n = 4 = 0, 1, 2, 3 m = -2,-1,0,+1,+2 (2) Disallowed: = 3 is disallowed when n = 3. (3) Disallowed: m l = 1 is disallowed when = 0. (4) Allowed: n = 4 = 0, 1, 2, 3 m l = -3,-2,-1,0,+1,+2,+3 (5) Disallowed. m s must be ± 1/2 , and cannot be -1. 5. All the alkaline earth metals in their ground states possess two s electrons in their valence shell. True or False? The answer is: True. Alkaline Earth elements (Be to Ra) have the valence electron configuration ns 2 , where n = 2, 3, 4, 5, 6, 7. 6. Sketch a cross-section of the 5 d yz orbital? Be sure to label your axis system and indicate phases (by + or –) on your drawing. 7. For which element(s) does the electron in the outermost occupied orbital have the quantum numbers n = 3 and = 1?
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CHEMISTRY 121 3 Department of Chemistry University of British Columbia The answers are: Al, Si, P, S, Cl, Ar The outermost occupied orbitals are ones with the largest values of n , i.e. the valence orbitals.
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9 - CHEMISTRY 121 Problem Set 9 Answer 1. Which of the...

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