AP Chemistry: Chemical Bonding & Molecular Structure 3 — Questions and Answers
Question 1: Which species is isoelectronic with the neon atom?
- F- (Correct answer)
- Cl-
- Na atom
- Mg atom
Correct answer: F-
F- gains one electron to reach 10 electrons, identical to neon's configuration.
Question 2: In molecular orbital theory, what is the bond order of the O2 molecule?
- 1
- 1.5
- 2 (Correct answer)
- 3
Correct answer: 2
O2 has a bond order of 2, calculated as (8 bonding - 4 antibonding)/2.
Question 3: Why is O2 paramagnetic, a property correctly predicted by molecular orbital theory but not by simple Lewis structures?
- It has all paired electrons
- It has two unpaired electrons in pi antibonding orbitals (Correct answer)
- It has a triple bond
- It contains an unpaired electron on each oxygen nucleus
Correct answer: It has two unpaired electrons in pi antibonding orbitals
MO theory places two unpaired electrons in the degenerate pi* antibonding orbitals, making O2 paramagnetic.
Question 4: Which of the following molecules is nonpolar despite containing polar bonds?
- NH3
- H2O
- CCl4 (Correct answer)
- HCl
Correct answer: CCl4
CCl4 has tetrahedral symmetry that causes the bond dipoles to cancel, making it nonpolar.
Question 5: What type of crystal lattice is found in solid sodium chloride?
- Molecular
- Covalent network
- Ionic (Correct answer)
- Metallic
Correct answer: Ionic
NaCl forms an ionic lattice of alternating Na+ and Cl- ions held by electrostatic attraction.
Question 6: Which compound is expected to have the greatest lattice energy?
- NaCl
- KCl
- MgO (Correct answer)
- CaO
Correct answer: MgO
MgO has the largest lattice energy because of its 2+ and 2- charges combined with small ionic radii.
Question 7: How many resonance structures contribute to the carbonate ion (CO3^2-)?
- 1
- 2
- 3 (Correct answer)
- 4
Correct answer: 3
The carbonate ion has three equivalent resonance structures from delocalizing the double bond among three oxygens.
AP Chemistry: Chemical Bonding & Molecular Structure 3
Which species is isoelectronic with the neon atom?