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Unformatted text preview: Version 384 Exam 2 mccord (50960) 1 This print-out should have 34 questions. Multiple-choice questions may continue on the next column or page find all choices before answering. 001 3.0 points An electron in a hydrogen atom moves from the n = 2 to n = 5 level. What is the wave- length of the photon that corresponds to this transition and is the photon emitted or ab- sorbed during this process? 1. 276 nm; absorbed 2. 1875 nm; emitted 3. 434 nm; emitted 4. 276 nm; emitted 5. 1875 nm; absorbed 6. 434 nm; absorbed correct Explanation: 002 3.0 points Carbon is the central atom in CH 2 O. The carbon and oxygen in CH 2 O, are joined by 1. two bonds. correct 2. four bonds. 3. two double bonds. 4. one bond. 5. three bonds. Explanation: The total number of valence electrons is C 1 4 e- = 4 e- H 2 1 e- = 2 e- O 1 6 e- = 6 e- 12 e- and the Lewis structure is H C O H 003 3.0 points Which of the following pairs of elements would be LEAST likely to form a compound by ionic bonding? 1. Al and F 2. C and N correct 3. Cs and O 4. Na and S 5. Mg and Br Explanation: The difference in electronegativity (0.5) is less than one between C and N, so this is the pair that would be least likely to form an ionic bond in its compound. 004 3.0 points 1 s 2 2 s 2 2 p 6 3 s 2 3 p 5 is the electron configura- tion for which one of the following ions? 1. S + 2. P 2- correct 3. P + 4. Cl- 5. P 2+ Explanation: We need an ion that has 2 + 2 + 6 + 2 + 5 electrons; i.e. , P 2- . 005 3.0 points Which do you think would be larger and why? The first ionization energy, IE 1 , of Ne, The second ionization energy, IE 2 , of Na 1. IE 1 of Ne, because Ne has a smaller radius Version 384 Exam 2 mccord (50960) 2 than Na. 2. IE 2 of Na, because Na + and Ne have the same electron configuration but Na has more protons than Ne. correct 3. IE 1 of Ne, because Ne is a noble gas and Na is an alkali metal. 4. IE 1 of Ne, because the electrons in Ne are not as well shielded from the nucleus as those in Na + . 5. IE 2 of Na, because Na + and Ne have the same number of protons, but Na + has fewer electrons than Ne. Explanation: The second ionization energy of Na is the ionization energy of Na + . Na + and Ne have identical electronic structures. They are both [He]2s 2 2p 6 . However, Na (and Na + has 11 protons and Ne only has 10. Therefore the electrons will be held more tightly onto Na + than Ne. 006 3.0 points The atomic number ( Z ), electronic configura- tion, and number of unpaired electrons for an ion are 52, [Kr] 5 s 2 4 d 10 5 p 5 6 s 1 , and 2, respec- tively. What are the element symbol, charge, and energy state for that ion? 1. Y; 2+; ground 2. Tc; 1+; excited 3. Sr; 1+; ground 4. Te; 2- , excited correct 5. Sr; 1+; excited 6. Sc; 1+; ground 7. Zn; 2+; excited 8. S; 2- ; ground Explanation: Z gives the number of protons in the neu- tral atom. The number of electrons is given by adding up the superscripts for the given electron configuration (dont forget the no-...
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- Fall '07