CH141f Study Guide - Midterm Guide: Antibonding Molecular Orbital, Atomic Radius, Isoelectronicity

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Published on 11 Oct 2018
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CH141 – Practice Exam 3 Page 1 of 9
Name: _______________________
Part I. Multiple Choice:
1. Which of the following pairs of atoms/ions is isoelectronic?
__ A. O–2, S–2
__ B. Na, Na+1
__ C. Br–1, Kr
__ D. Cu, Zn
__ E. none of these
2. Which of the following quantum number sets describes a 4f orbital?
__ A. n=2, l=0, ml= 0
__ B. n=3, l=1, ml= -1
__ C. n=3, l=2, ml= -1
__ D. n=4, l=2, ml= +1
__ E. n=4, l=3, ml= +2
3. Which element below has the largest atomic radius?
__ A. S
__ B. P
__ C. N
__ D. B
__ E. F
4. Which element below has the highest electronegativity?
__ A. C
__ B. P
__ C. N
__ D. B
__ E. Be
5. Order the elements S, Cl, and F in terms of increasing atomic radii.
__ A. S, Cl, F
__ B. Cl, F, S
__ C. F, S, Cl
__ D. F, Cl, S
__ E. S, F, Cl
6. Which of the following statements is true?
__ A. Electrons are never found in an antibonding MO.
__ B. All antibonding MOs are higher in energy than the atomic orbitals of which they are composed.
__ C. Antibonding MOs have electron density mainly outside the space between the two nuclei.
__ D. None of the above is true.
__ E. Two of the above statements are true.
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CH141 – Practice Exam 3 Page 2 of 9
Part II. Short Answers and Calculations To get full credit you must show all your work!
7. Give the electron configuration for the following atoms and ions (condensed notation is OK).
Zr __________________________________________
V+3 __________________________________________
8. Circle the correct answer for each of the following:
a) The lowest (least endothermic) 1st ionization energy: Li, Na, Mg
b) The greatest (most exothermic) electron affinity: As, Se, Br
9. Rank the following orbitals in an atom of hydrogen from lowest to highest energy (list them below in
order using the < symbol and the = symbol if any orbitals are the same energy): 1s, 2s, 2p, 3s
lowest energy highest energy
10. Rank the following orbitals in an atom of sodium from lowest to highest energy (list them below in
order using the < symbol and the = symbol if any orbitals are the same energy): 1s, 2s, 2p, 3s
lowest energy highest energy
11. How many electrons can be accommodated in the n = 4 quantum shell? ________
12. In one sentence, clearly explain why NO has a small bond dipole (polar compound) and the oxygen
has a partial negative charge. You can draw a picture to support your answer.
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CH141 – Practice Exam 3 Page 3 of 9
13. In one sentence, clearly explain why CO has a small bond dipole (polar compound) and the oxygen
has a partial positive charge. You can draw a picture to support your answer.
14. In one sentence, clearly explain why MgO has a much higher lattice energy than NaF.
15. For laughing gas, N2O
a) Draw a valid Lewis structure below (connectivity N–N–O). Assign formal charges to all atoms.
b) Draw two additional resonance structures of the structure you drew in part (a). Assign formal charges
to all atoms.
c) Circle the single structure above (from the three structures in parts (a) and (b)) that most closely
represents the true structure of N2O and briefly explain your choice.
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