Chemistry 121

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Chemistry 121

• Week 9 Molecular shape polarity

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2 electron groups
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3 electron groups
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4 electron groups
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5 electron groups
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6 electron groups
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Check-in

• SeO2
• BeCl2
• PBr3
• BCl3

SeO2 and BeCl2 each have one central atom that is
bonded to two other atoms, but they have
different shapes.  Why? 
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Measuring dipole moment
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Dipole moments
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Check-in

• The molecule H2S has a dipole moment of 0.97 D. 
  Is the molecule linear or bent?  Why?
•  A molecule with the formula EF3 has a dipole
  moment of 2.59 D.  Is the molecule trigonal
  pyramidal or trigonal planar?  Why?
• Based on the dipole moment, what is the most
  likely identity of the central atom, E  B, As,
  or Br?  Explain your choice briefly 

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Molecular shape and dipole moment
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Practice!

• Draw Lewis structure
• Include resonance structures when appropriate
• Calculate formal charges
• Determine molecular shape and assign bond angles
• Predict polarity
• Draw net dipole when appropriate