In most amines, the nitrogen atom is sp³ hybridized, with a pyramidal structure and bond angles close to 109°. In urea, both nitrogen atoms are found to be planar, with bond angles close to 120°. Explain this surprising finding. (Hint: Consider resonance forms and the overlap needed in them.)

a. Which of the species have bond angles of 109.5°?

b. Which of the species have bond angles of 120°?

H₂O H₃O^{+ +}CH₃ BF₃

Do the sp² carbons and the indicated sp³ carbons lie in the same plane?

For each of the following molecules, indicate the hybridization of each carbon and give the approximate values of all the bond angles:

a. CH₃C≡CH

Predict the hybridization and geometry of the carbon and nitrogen atoms in the following molecules and ions. (Hint: Resonance.)

a.

b.

c.

Predict the hybridization, geometry, and bond angles for the carbon and nitrogen atoms in acetonitrile (CH₃–C≡N:).

Describe the orbitals used in bonding and the bond angles in the following compounds:

e. BF₃

Predict the approximate bond angles in

a. the methyl cation.

b. the methyl radical.

c. the methyl anion.

Predict the approximate bond angles for the following:

c. the C—C—N bond angle in CH₃C≡N

d. the C—C—N bond angle in CH₃CH₂NH₂