Pre-AP CHEM Unit 5 Day 4 Review

The electron geometry is the same as the molecular shape when there are no lone pairs of electrons on the central atom.

• True
• False
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The basic fact that determines molecular shapes is that

• nuclei attract each other.
• electron pairs attract each other.
• electron pairs repel each other.
• nuclei repel each other.

Lone pairs around the oxygen atom of a water molecule play no role in determining its molecular geometry which has what shape?

• True;
  bent
• False;
  bent
• True;
  linear
• False;
  linear

The bond angle in NH₃ is __________ than the bond angle in CH₄ because

• LARGER; the unshared pair of electrons on nitrogen is LESS repulsive to the bonded electron pairs.
• SMALLER; nitrogen has a SMALLER atomic radius than carbon.
• LARGER; nitrogen has a LARGER atomic radius than carbon.
• SMALLER; the unshared pair of electrons on nitrogen is MORE repulsive to the bonded electron pairs.

Which of the following most likely represents the molecular geometry of water?

• A
• B
• C
• D

Which of the following molecules do NOT match their molecular geometry?
I. BeH₂: bent
II. NH₃: trigonal pyramidal
III. CF₄: tetrahedral
IV. NH₄⁺: tetrahedral

• I only
• I and II only
• II, III, and IV only
• All are paired correctly.

Water has a bent molecular geometry because

• there are unpaired electrons within the bonds.
• the two O-H bonds repel each other.
• oxygen does not have d-orbitals to allow for an expanded octet.
• there are 4 electrons on the oxygen atom which are not in the O-H bonds but which affect molecular shape.

Lewis structures can sometime be deceptive when determining molecular shape because they are drawn in two-dimensions.  Examine the Lewis structures. Which is not linear and why?

• CO₂ because it has double bonds
• BeCl₂ because beryllium is an exception to the octet rule
• H₂S because it has lone pairs on the central atom
• All are linear

Use VSEPR theory to predict the molecular shape of the molecule SeF₆.

• tetrahedral
• octahedral
• trigonal-planar
• trigonal-bipyramidal

What is the name of the molecular geometry shown below? (The dark circle and each white circle represent an atom.)

• trigonal pyramidal
• bent
• tetrahedral
• octahedral

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