5.09 – Molecular Shapes & Polarity

Today we will begin looking at the way molecules come together and form the specific shapes that influence their external bonding.

Lesson Objectives

  • Predict the three-dimensional shapes of molecules using the VSEPR model. (9.2)
  • Determine whether a molecule is polar or nonpolar based on its geometry and the individual bond dipole moments. (9.3)

Start exploring these ideas by going through the Molecule Shapes Simulation  (Web view).  Type out all responses and paste images into that document.

To become familiar with the topics presented in this mission, view the slides below and take note of the key ideas.  These are from section 9.1-9.3 of your text.

Now work through the practice problems, and post your work to OneNote.

Work out these mastery problems and check your answers in OneNote.  Post your work when finished, including any corrections.  These questions are from the text and a released AP Exam.

9.35    Predict whether each of the following molecules is polar or nonpolar.  Justify the response with Lewis structures.

(a) IF

(b) CS2

(c) SO3

(d) PCl3

(e) SF6

(f) IF5


9.97    Sulfur tetrafluoride (SF4) reacts slowly with O2 to form sulfur tetrafluoride monoxide (OSF4) according to the following unbalanced reaction:

SF4(g) + O2(g) → OSF4(g)

The O atom and the four F atoms in OSF4 are bonded to a central S atom.

(a) Balance the equation.

(b) Write a Lewis structure of OSF4 in which the formal charges of all atoms are zero.

(c) Use average bond enthalpies (Table 8.4, from 5.08 mastery) to estimate the enthalpy of the reaction. Is it endothermic or exothermic?

(d) Determine the electron-domain geometry of OSF4, and write two possible molecular geometries for the molecule based on this electron-domain geometry.

(e) Which of the molecular geometries in part (d) is more likely to be observed for the molecule? Explain.


2010 FRQ #5


Phenomenal work on those shapes Visitor!  Now we can look into how those valence electrons can be used as discrete regions when we know s and p orbitals should overlap.

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