# HW4answers - Cheung Anthony Homework 4 Due Oct 5 2006...

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Cheung, Anthony – Homework 4 – Due: Oct 5 2006, midnight – Inst: McCord 1 This print-out should have 38 questions. Multiple-choice questions may continue on the next column or page – find all choices before answering. The due time is Central time. 001 (part 1 of 1) 10 points How many nodal planes and/or nodal cones are expected for 2 s and 4 f orbitals, respec- tively? 1. 0 and 4 2. 1 and 4 3. 0 and 3 correct 4. 2 and 4 5. 1 and 3 Explanation: The 2 s orbital only has one radial node, but not a planar nor a conical node. The 4 f orbitals all have a total of 3 nodal planes or cones. 6 of the 7 4 f orbitals have 3 nodal planes while the last one ( d z 3 ) has 2 nodal cones and 1 nodal plane (for a total of 3). 002 (part 1 of 1) 10 points The C + cation has how many total electrons and how many valence electrons? 1. 6; 6 2. 6; 5 3. 5; 4 4. 7; 5 5. 6; 3 6. 6; 4 7. 7; 6 8. 7; 8 9. 5; 3 correct Explanation: C + has lost one electron, giving it 5 total electrons and 3 valence electrons. 003 (part 1 of 1) 10 points Write the electron-dot notation for the ele- ment Cl. 1. Cl 2. None of these 3. Cl 4. Cl 5. Cl 6. Cl correct 7. Cl 8. Cl 9. Cl Explanation: According to its electron configuration ([Ne] 3 s 2 3 p 5 ), Cl has 2 + 5 = 7 valence elec- trons, so the electron-dot notation for Cl is Cl 004 (part 1 of 1) 10 points Which lattice energy is larger? 1. rubidium chloride 2. lithium chloride correct Explanation: The Li + ion (58 pm) is smaller than the Rb + ion (149 pm). Because the lattice energy is related to the coulombic attraction between the ions E 1 r , the larger rubidium ion will have the lower lattice energy for a given anion. lithium chloride : 861 kJ/mol rubidium chloride : 695 kJ/mol

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Cheung, Anthony – Homework 4 – Due: Oct 5 2006, midnight – Inst: McCord 2 005 (part 1 of 1) 10 points What is the formula for the simplest, stable compound formed from lithium and oxygen? 1. Li 2 O correct 2. LiO 3. LiO 2 4. Li 2 O 2 Explanation: A lithium atom will lose one electron to form Li + . An oxygen atom will gain two electrons to form O 2 - . We need two Li + for every O 2 - to equalize the charge, so the ratio of lithium to oxide ions is 2:1, and the formula for lithium oxide is Li 2 O. 006 (part 1 of 1) 10 points Which of the following pairs of elements would be LEAST likely to form a compound by ionic bonding? 1. Al and F 2. Na and S 3. Cs and O 4. C and N correct 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. 007 (part 1 of 1) 10 points In reactions to form ionic compounds, non- metals generally 1. lose electrons. 2. become metals. 3. do not react. 4. gain electrons. correct Explanation: 008 (part 1 of 1) 10 points The phosphorous anion (P - ) has how many total electrons and how many valence elec- trons?
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