1. A Review of General Chemistry

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

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

NH₃ ⁺NH₄ ^-CH₃

In pent-2-yne (CH₃CCCH₂CH₃), there are four atoms in a straight line. Use dashed lines and wedges to draw a three-dimensional representation of this molecule, and circle the four atoms that are in a straight line.

You drew the Lewis structures of the following compounds and ion in Assessment 2.32. Predict their shapes around the central atom based on the Lewis structure.

(c) HCO₂H

Predict the approximate size of the following bond angles.

(d) the C—N—C bond angle in a quaternary ammonium salt

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

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

a. CH₃O^-

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.)

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

c. H₂CO

Predict the hybridization of the oxygen atom in water, H₂O. Draw a picture of its three-dimensional structure, and explain why its bond angle is 104.5°.