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Exam 3A KEY - tramw—(please print as name appears on UNC...

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Unformatted text preview: tramw— (please print as name appears on UNC roll) 1A. (4 pts) Write the full electron configuration for Pb, Z=82 (do NOT use noble gas shorthand). l‘sZZszzbasta “452501‘2‘65240W6 ‘(oszéi Hal/W" B. (4 pts) What is the predicted stable form of its ion? A) +1 ' B) +2 ' C) -—4_ BOV ' D) +4 E) +14 Explain your answer using electron configurations. [90M haw [Av] av [86 ' 2A. (6 pts) Which species is larger (circle one I) or K+ firm k+ “H B. Which concept explains the size differ : E’. A) p electrons are slightly higher in : ergy than s electrons in the same shell. B) Nuclear charge. C) Repulsion when two electron -. occupy the same orbital. D) A screening effect by the in I er electrons. 3. (4 pts) Give a set of four qu turn numbers for the highest energy electron in calcium. 4: n: 4 I: {’1 - ml: 9 ms=+’/z- OV'IZ— 4A. (2 pts) How m .- ny unpaired electrons are in the ground state Mo atom (2:42)? ‘ m Wag (ml...) B. (4 u 5) Write the electron configuration for Mo+ using noble gas shorthand. cm 415’ £12515 f 6" Name iflA (please print as name appears on UNC roll) ’euo‘hz 5 + éblock 5. (2 pts) The periodic table of known elements consists of s, p, d, and f blocks. If an of elements existed, how many elements across would this block be? 22+ l=# Olbotals =11 Orbduig - a X 2 e‘/ov~launl =22 damth 6. '(6 pts) For the ground state of platinum, Pt (2:78): A) how many electrons have m3 = +112? a la b (o B) how many electrons occupy p orbitals? 2P C) how many electrons occupy atomic orbitals with n=4? LleMpdeLtP‘l 7. (4 pts) Which of the following orbital designations islare acceptable for the electron in a hydrogen atom? -————-—- 15 5f 7d 93 [if 69L hsb’ £1:th is 6t: ’14 Q5 lo 8. (5 pts) An oxygen atom has the following electron configuration: 1s2 252 2px2 szz. Is this a ground state or an excited state atom? Explain. Exam state has t’ pamd (M Zpe .0 297 Wold amp . 2 I (brow/Id 810% a 224229: 29" 2P2 mum to] alga/mi? g 14 +H’ 9. (4 pts) For an atom of silicon, what is the effective nuclear charge felt by: A) the valence electrons +fl 2” Com = Z —- {O B) the n=2 electrons ‘HZ Z "“ 28 ’ 4 4‘ 4‘ j"? q‘ '7' __i<_E_:_____ k at F LS e 1': P I‘gr"::lrr:aeise print as na\rr/1e afiars on UNC roll) 3 10A. (6 pts) Which atom has a greater first ionization energy (circle one) or Se B. Which concept accounts for this difference: A) p electrons are slightly higher in energy than s electrons in the same shell. B) Repulsion when two electrons occupy the same orbital. ' C) A screening effect by the inner electrons. D) Zetf- 11. (4 pts) Rank the following atoms in order of increasing size: Al, Si. Ga, Ge. A4 Si, .. 31? AU ee< GO.) Gm 62¢. 12. (6 pts) From the list of elements {Se, 0, i, P, B] choose two elements that, when combined: A) form the most polar covalent bond: B “O F. B) form the longest single bond: & -- _L 0) form a compound of formula XYZ: & i J.- 50 —-, 0 13A. (6 pts) Rank the following species in order of increasrng bond length: NO" No+ 0F" 60 1’ \L “0“<~0“<0F“ cit-50:71: B. (4 pts) What is the formal charge on each atom in NO'? : "' Pam) = 6-2—4: -1 Eggéj — l31(0): 6—2—4; = g5 Name I "' E (please print as name appears on UNC roll) 14. (4 pts each) Draw a single valid Lewis structure for each of the following; draw a box around your final answer: A) HN03 B) OFz . .C) IF3 |+6+ig=24r (Mil-H206“ 7+Zl=%e" NéO‘I - db__ i ail." . - 2E: 15. (8 pts) Estimate the heat of reaction for following reaction: N2 + 3 0'2 —) 2 NCI3 Bond Bond enthalpy , -* v .. kJ/mol :NaNz -.Cl—-C‘J= N Im- .. ~ “ / \.. Im- Ci l Cl nat- ' :C\= Aw 29mm» » ipfivwmol) g 9mm) + 239mm!) —- loD(N’C|) AHVHQI ltd = 1341+ gem—“(4200 K) = 4AM l4) Name I " A (please print as name appears on UNC roll) 16. (4 pts) Rank the following ionic compounds in order of increasing lattice energy: ' MgO CaS NaCl Csl CsI< NaCl < CaS< MO 17. (8 pts) The diagram below is the Born-Huber cycle for the formation of crystalline potassium fluoride. mg) 4» 112F2®+2 Ktsge mask K _ Wits) Which step (e.g.,- #1), as labeled in the diagram, has an energy change with the same magnitude as the following process: ' A) the electron affinity of fluorine? B) one~half the bond enthalpy of molecular fluorine? C) the lattice energy of potassium fluoride? D) the heat of formation of potassium flouride? thigh ...
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