Tutorial 3 a - CHEM 1A03 TUTORIAL#3 September 28-October 2...

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CHEM 1A03 TUTORIAL #3 September 28-October 2, 2009 Solutions – Chapter 9 _____________________________________________________________________ Page 1 of 4 The following problems (1-8) are based on material from Chapter 9. 1) What is the general electronic configuration (where n = principal quantum number) that best describes the halogens as a group. A) ns 1 np 6 B) ns 2 np 4 C) ns 2 np 5 D) ns 2 np 6 E) ns 2 np 3 Answer: C. The halogens are characterized by having 5 electrons in the p subshell, in the ground state. For more information check Petrucci’s Section 9-2. 2. a) Which of the following gaseous atoms is smallest : P, Cl, Ca, or Si? The atoms Si, P, and Cl are in period 3; Cl is the smallest of these three, since size decreases across a period (as effective nuclear charge increases). Ca is in period 4, and is larger than any of the above-named three atoms. Thus Cl is the smallest . b) Which of the following gaseous atoms has the highest ionization energy : Li, Ne, Na, Ar? Ne has the highest ionization energy. The noble gases have very high ionization energies and the alkali metals have the lowest ionization energies (general trend: ionization increases across a row, with some exceptions). Also, I.E.(Ne) > I.E.(Ar), since the valence electrons of Ne are closer to the nucleus. In both Ne and Ar the core charge is +8. 3. Arrange the following gaseous ions in the order of decreasing ionic radius (from largest radius to smallest radius) : S 2 , K + , Ca 2+ , Cl S 2- > Cl - > K + > Ca 2+ , where > means "larger than". All four of these species have the electron configuration [Ne] 3s 2 3p 6 , thus they are all isoelectronic with Ar. For such an isoelectronic series the only difference is the charge on the nucleus. The higher the nuclear charge, the smaller the size, since there is a greater attraction for the electrons. The nuclear charges (atomic numbers, Z) for S, Cl, K and Ca are 16, 17, 19 and 20 respectively. S 2 is the largest, Ca 2+ is the smallest.
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CHEM 1A03 TUTORIAL #3 September 28-October 2, 2009 Solutions – Chapter 9
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This note was uploaded on 01/16/2010 for the course CHEMISTRY 1A03 taught by Professor Dr.p.lock during the Fall '08 term at McMaster University.

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Tutorial 3 a - CHEM 1A03 TUTORIAL#3 September 28-October 2...

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