WS3 QM solutions - worksheet 3 PDF

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WS3: Chapter 13

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1. Draw the Lewis dot structure for PCl3. What is the molecular shape and electron pair geometry of this species? Electron Pair Geometry: Tetrahedral Molecular Shape: Trigonal Pyramidal (AX3E)

2. Draw the Lewis dot structure for [HSO4]1-. How many resonance structures does it exhibit? For the “central” (i.e. non-terminal) atoms, what is the molecular shape, and electron-pair geometry? There are many possible Lewis structures that satisfy the octet rule (or expanded octet for Sulfur) that can be drawn, but most don’t contribute substantially due to excessive nonzero formal charges. The election-pair geometry is tetrahedral around both the non-terminal oxygen and the sulfur. The molecular shape is tetrahedral (AX4) for the sulfur and bent (AX2E2) for the non-terminal oxygen.

This structure gives S a +2 formal charge (FC), and 3 oxygens -1 FC

This structure (plus 2 equivalent resonance structures) gives S a +1 FC, and 2 of the oxygens a -1 FC

This structure (plus 2 equivalent resonance structures) gives only a single oxygen a -1 FC. This structure contributes most to the reality of the hydrogen sulfate (bisulfate) ion’s bonding. 1

This structure gives sulfur the -1 FC, even though oxygen is more electronegative.

This structure gives oxygen a positive FC, making it even less desirable than the first structure.

3. Give the Lewis structures (with all resonance structures identified) for the following: H2S, SO32-, CH2Br2, HCN, and CO. (a) H2S

(b) SO3 2-

(c) CH2Br2

(plus 2 equivalent)

2

(d) HCN

(e) CO...