U2.7 · VSEPR and Bond HybridizationPractice · VSEPR 与杂化
Lessons covered:U2.7 VSEPR and Bond Hybridization
- 1Multiple choice
What is the shape of the chlorate ion, ?
ExplanationTotal valence electrons = 7 + 3 × 6 + 1 = 26. The three Cl–O bonds use 6, three lone pairs on each O use 18, and the last 2 form a lone pair on Cl. Cl has 3 bonded atoms + 1 lone pair = 4 electron domains in a tetrahedral arrangement; ignoring the lone pair, the ion is trigonal pyramidal. Seeing “three O atoms” and choosing trigonal planar is the trap.
- 2Multiple choice
What is the hybridization of the three carbon atoms in acetone, ?
ExplanationCount the electron domains on each C (bonded atoms + lone pairs). Each end carbon is bonded to 4 atoms: 4 domains, sp³. The middle C is bonded to two C atoms and one O (the C=O double bond counts as one domain): 3 domains, sp². Only the σ part of a double bond sets the hybridization; the other bond is a π bond.
- 3Numeric
How many σ bonds are in one benzene molecule, ?
σ bondsExplanationEvery pair of bonded atoms has exactly one σ bond: 6 C–C bonds + 6 C–H bonds = 12 σ bonds. In one Kekulé structure, each of the 3 C=C double bonds also has a π bond, for 3 π bonds. Counting only the 6 C–C bonds misses the C–H bonds.
- 4Multiple choice
According to VSEPR, in which molecule are the F–X–F bond angles less than 109.5° but greater than 90°?
ExplanationFind the shapes first: trigonal planar, trigonal pyramidal, tetrahedral, T-shaped. is 120°, and is exactly 109.5°. In , P has 3 F atoms and 1 lone pair in a tetrahedral arrangement; the lone pair repels the bonding pairs more strongly and squeezes the angle below 109.5°. is T-shaped, with F–Cl–F angles near 90° (slightly less) and 180°.
- 5Select all
Which of these molecules are nonpolar?
More than one option may be correct. Choose all that apply, then press Submit.
Explanationtetrahedral; trigonal pyramidal; linear; tetrahedral; bent. (tetrahedral) and (linear) have identical outer atoms arranged symmetrically, so the bond dipoles cancel: nonpolar. (trigonal pyramidal) and (bent) have lone pairs and aren’t symmetric. is tetrahedral too, but C–H and C–Cl bonds have different polarities that don’t cancel (dipole moment 1.6 D).
- 6Multiple choice
The graph shows the H–X–H bond angles in , , and (note that the axis starts at 100°). Which best explains why the angle decreases?
ExplanationRead the bars: 109.5° → 107° → 104.5°. Each central atom has 4 electron domains (tetrahedral electron geometry), with 0, 1, and 2 lone pairs. A lone pair is held by only one nucleus, takes up more room, and repels bonding pairs more strongly, squeezing the H–X–H angle; more lone pairs squeeze it more. The central atoms C, N, and O get smaller, not larger.
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