exam1 - Chemistry 301 Spring, 2010 -1- EXAM #1 February 10,...

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Chemistry 301 -1- EXAM #1 Spring, 2010 February 10, 2010 Total Pts. ______ NAME: ____ KEY ______________________________ There are 14 problems on 4 pages plus an information sheet (#9 and #11 have greatest weight). Show work to receive full credit. Write legibly and work independently. (1) (2 pts) For multi-electron atoms, briefly explain why the energy of the 3 s atomic orbital is lower than the energy of a 3 p atomic orbital. Screening (shielding): the 3 s AO penetrates to the nucleus more than the 3 p AO. (2) (2 pts) How many radial nodes does a 4 p atomic orbital have? _____ 2 ______ n = 4, l = 1: # radial nodes = n l – 1 = 4 – 1 – 1 = 2 nodes (3) (4 pts) Draw a 3 d xy atomic orbital. On your drawing, include Cartesian ( x -, y -, z -) axes and label all nodal surfaces. x y Nodes (4) (6 pts) Arrange the following subshells in order (from left to right) of increasing energy for a neutral atom: 4 d , 5 s , 3 p , 6 p , 5 d , 4 f __ 3 p __ < __ 5 s __ < __ 4 d __ < __ 4 f __ < __ 5 d __ < __ 6 p __ (4) (5) (6) (7) (7) (7) Energy increases as n + l (5) The ground state electronic configuration for Gd (Z = 64) is [Xe](4 f ) 7 (6 s ) 2 (5 d ) 1 . (a) (2 pts) What configuration would be expected for Gd if the aufbau principle were applied? [Xe] (6 s ) 2 (4 f ) 8 (b) (2 pts) Briefly explain why the observed ground state configuration differs from your answer in (a). (4 f ) 8 is more than half-filled, so to minimize e ! -e ! repulsion, one electron is promoted into the 5 d subshell, which would have a slightly higher orbital energy. (6) (4 pts) The general trend for ionization energies is to increase from left to right across a period. Briefly explain why the first ionization energy of Ga (5.10 eV) is lower than that for Zn (9.39 eV). Ga ionizes from the 4 p subshell; Zn ionizes from the 4 s subshell.
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Chemistry 301 -2- EXAM #1 Spring, 2010 February 10, 2010 Total Pts. ______ (7) (2 pts)
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exam1 - Chemistry 301 Spring, 2010 -1- EXAM #1 February 10,...

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