PILOT EXAM 2 Answer Key - Chapters3and4 Name No of points 1...

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Name: ………………………….…….              Answers to   Chem 111 Pilot Exam Nr 2                                                   Chapters 3 and 4 No of points 1. Atom of which of the following elements needs to lose two valence electrons to achieve the noble gas configuration? a) Na b) Si c) Ba d) S [4] Na atom needs to lose 1 e, Si 4 e's (hard to accomplish), S needs 6 e's, but this is extremely hard to accomplish as it would require so highly electronegative element that does not exist) 2. Atom of which of the following elements needs to gain one valence electron to achieve the noble gas configuration? …………………………………………………. .…. .…………. [4] a) Ca b) Al c) S d) Br Ca and Al are elements which are not capable of gaining e'. S needs to gain 2e'. Br needs to gain 1e. 3. To gain a noble gas configuration an atom of aluminum must [4] a) lose one electron b) lose three electrons c) gain one electron d) gain three electrons Al atom has 3 valence electrons. By losing them it achieves the electron configuration of Ne 4. At each of the following elements write its most stable ion Ca Ca 2+ Na . .. Na + S .… S 2- ….. F … F - [8] Note that less electronegative elements are losing e's while more electronegative elements are gaining e's. 5. Which ion should be the most stable a) Cl 2- b) Na 2+ c) Ba 2+ d) Al 2+ ………. . [4] Only Ba 2+ has an electronic configuration of noble gas, Cl 2- , Na 2+ Al 2+ are unrealistic. Far from noble gas configuration. Note that Na + , Cl - and Al 3+ are all ions having noble gas configuration 6. Sodium chloride consists of a) molecules of NaCl b) atoms of Na and Cl c) Na + and Cl - ions [4] Start from establishing the type of bond . Due to the large difference in electronegativity we are dealing with ionic bond. . Consequently there are no molecules of NaCl nor Na and Cl atoms. We could possibly say; Na and Cl atoms but it would be necessary to add: ionized atoms which is equivalent to …ions 7. Write the formula of the ionic compound formed from a) Aluminum and Oxygen Al 2 O 3 .. b)
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This note was uploaded on 10/28/2010 for the course CHEM 111 taught by Professor Polaski during the Winter '08 term at Central Washington University.

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PILOT EXAM 2 Answer Key - Chapters3and4 Name No of points 1...

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