Homework Help

Which of these bond angles is the largest?A  Cl–B–Cl in BCl_3 B  H–N–H in...

user profile pic

roshan-rox | Valedictorian

Posted May 31, 2013 at 12:09 PM via web

dislike 0 like

Which of these bond angles is the largest?
A  Cl–B–Cl in BCl_3

B  H–N–H in NH_3

C  Cl–Be–Cl in BeCl_2

D  H–O–H in H_2O

1 Answer | Add Yours

Top Answer

user profile pic

mvcdc | Student, Undergraduate | (Level 1) Associate Educator

Posted May 31, 2013 at 1:05 PM (Answer #1)

dislike 2 like

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.

Sources:

Join to answer this question

Join a community of thousands of dedicated teachers and students.

Join eNotes