Assignment 4: Lewis Structures & Formal Charges PDF

# Assignment 4 ## 1. Draw all possible Lewis structures for the following molecules: - PCI3 - OCI- - NH3 - HF - CF4 ## Deficiency - N2 - NO+ ## Octet deficient - BF3 - BeH2 ## Expanded octet - SF6 - XeF2 - CIF3 - ICl4 ## Resonance forms - NO3 - O3 - NO2 ## Formal Charge - NC...

# Assignment 4 ## 1. Draw all possible Lewis structures for the following molecules: - PCI3 - OCI- - NH3 - HF - CF4 ## Deficiency - N2 - NO+ ## Octet deficient - BF3 - BeH2 ## Expanded octet - SF6 - XeF2 - CIF3 - ICl4 ## Resonance forms - NO3 - O3 - NO2 ## Formal Charge - NCO- - CO2 - OCS ## 2. MCQs: a) The total number of lone pairs in NCI3 is: 1) 6 2) 8 3) 9 4) 10 5) 13 b) The best Lewis structure for CS2 is: 1) C=S-S 2) S-C-S 3) S=C=S 4) S=C-S c) In the Lewis structure of ICl2, how many nonbonding pairs (lone pairs) of electrons are around the central iodine atom: 1) 0 2) 1 3) 2 4) 3 5) 4 d) The number of resonance structures for sulfur dioxide SO2 that satisfy the octet rule is: 1) 1 2) 2 3) 3 4) 4 5) None of these e) Which of these statements is a useful guideline for the application of formal charges in neutral molecules? 1) A Lewis structure with no formal charges on most of its atoms is preferred. 2) Lewis structures with large formal charges (e.g., +2, +3 and/or -2, -3) are preferred. 3) The preferred Lewis structure is one in which positive formal charges are on the most electronegative atoms. 4) The preferred Lewis structure is one in which negative formal charge is on the central atom. 5) (A) and (D). f) What is the formal charge on sulfur in the best Lewis structure for the SCN- (thiocyanate) ion? 1) +2 2) -2 3) +1 4) -1 5) 0 g) Select the molecule(s) that fits the statement “These molecules violate the octet rule” I. BF3 II. CHBr3 (C is the central atom) III. Br2 IV. XeCl2 V. CO VI. SF4 1) I, II, IV 2) I, III, IV, VI 3) III, V, IV 4) I, IV, VI 5) I, II, IV, VI ## 3. Challenging questions: a. Draw all possible Lewis structures for SO₄¯² and decide which is the most favorable structure. b. The best Lewis structure for chlorate ion ClO3¯, should show _single bond(s)_, _double bond(s)_, and _lone pair(s)_. 1) 2, 1, 10 2) 3, 2, 10 3) 1, 2, 8 4) 2, 1, 9