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Which of these bond angles is the largest?A Cl–B–Cl in BCl_3 B H–N–H in...
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To determine the largest bond angle, we could determine the molecular geometry of each species first.
`BCl_3` : Boron is connected to three chlorines through single bonds. Since boron only has three valence electrons, the three single bonds already account for them - no lone pair. Hence, the shape is trigonal planar with a bond angle of 120 degrees.
`NH_3` : Like boron trichloride, nitrogen is attached to the hydrogens through single bonds. However, nitrogen has 5 valence electrons and hence still has a lone pair (an additional electron domain). The shape of this molecule is trigonal pyramidal with bond angle of 107 degrees.
`BeCl_2` : Beryllium has two valence electrons, attached through single bonds to two chlorines. The shape is thus linear with bond angle of 180 degrees.
`H_2O` : Oxygen has six valence electrons. Two of these are used to form single bonds with the two hydrogens. Hence, there are still four electrons - these constitute two lone pairs. Hence, we have two bonded domains, and two electron pairs. Water is a bent molecule so the angle is 109.5 degrees.
Given these, we see that beryllium chloride has the largest angle at 180 degrees. Answer is C.
Posted by mvcdc on May 31, 2013 at 1:05 PM (Answer #1)
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