Chemistry 1A - Spring 2010 - Nitsche - Midterm 2 Solutions

Chemistry 1A - Spring 2010 - Nitsche - Midterm 2 Solutions...

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Chemistry 1A, Spring 2010 Midterm 2 Solutions Mar 8, 2010 Problems 1. Which atom has the lowest ionization energy? C) Li (1s 2 4p). This will have the lowest ionization energy, because the 1s electrons will shield most of the nuclear charge, so the 4p electron only sees about +1 effective nuclear charge. The 3p electron in He(1s3p) also will see about +1 effective nuclear charge, but it is in a lower energy orbital, so it will require more energy to ionize. 2. [Ar]4s 2 3d 10 4p 3 is the electron configuration of a(n) atom. A) As 3. Which one of the following configuration depicts an excited oxygen atom? B) 1s 2 2s 2 2p 2 3s 2 . This is the only oxygen configuration (8 electrons), other than the ground state ( 1s 2 2s 2 2p 4 ) . 4. Which two elements have the same ground-state electron configuration? E) No neutral elements have the same ground state electron configuration 5. Which of the following will become more paramagnetic upon ionization to form a +1 ion? Mark all that apply A) O, C) Br, D) Pd All of these have paired electrons in their ground state configuration. Therefore, they will have a greater number of unpaired electrons upon ionization, making them more paramagnetic. The next three questions refer to three reactions shown below. The energy diagram has one column which shows the relative energies of products and reactants for each reaction. Ar Ar + + e - Cs + + e - Cs Ge Ge + + e - 1
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I: Cs II: Cs + + e - III: Ge E Ge + + e - IV: Ar + + e - Ar These are all ionization energies. Therefore, the highest energy difference is for Ar, because it has the highest ionization energy, followed by Ge, and finally Cs. 6. Which is the appropriate label for level I in the diagram? A) Cs 7. Which is the appropriate label for level III in the diagram? E) Ge 8. Which is the appropriate label for level IV in the diagram? D) Ar + + e - 9. What is the P-O bond order in PO 3 - 4 ? D) 1 1 4 . .. .. P O O O O .. .. .. .. .. .. .. .. .. 3- .. P O O O O .. .. .. .. .. .. .. .. 3- P O O O O .. .. .. .. .. .. .. 3- .. .. P O O O O .. .. .. .. .. .. .. 3- The Lewis structure for PO 3 - 4 will have 1 P-O double bond and 3 P-O single bonds, since phosphorus can expand its octet. This will give it 4 resonance structures, and thus average bond order is 1 1 4 10. Which of the following elements has the largest electronegativity? B) antimony 2
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11. Of the following, which gives the correct order for atomic radius for Mg, Na, P, Si and Ar? D) Na > Mg > Si > P > Ar 12. Which isoelectronic series is correctly arranged in order of increasing radius? D) Ca 2+ < K + < Ar < Cl - These all have the same electron configuration, therefore the atom with the largest nuclear charge will have the smallest radius, and the atom with the lowest nuclear charge will have the largest radius. 13. According to Lewis theory, what is wrong with this structure for hydrogen cyanide, HCN? HCN E) All of the above (hydrogen cannot accommodate more than 2 electrons, nitrogen does not have an octet, carbon does not have an octet, there are not enough electrons in the structure).
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Chemistry 1A - Spring 2010 - Nitsche - Midterm 2 Solutions...

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