Unit Quiz
Quiz Instructions
This quiz assesses your understanding of chemical bonding concepts. Complete all 10 questions without notes first.
Topics Covered
- Ionic vs. covalent bonds
- Lewis structures
- Molecular geometry
- Polarity and properties
Scoring Guide
- 9-10 correct: Excellent - Ready for Chemical Reactions!
- 7-8 correct: Good - Review missed concepts
- 5-6 correct: Fair - Additional practice needed
- Below 5: Review the unit before retaking
Quiz Questions
Question 1: What type of bond forms between sodium (Na) and chlorine (Cl)?
Answer: Ionic bond
Na is a metal that loses an electron, Cl is a nonmetal that gains an electron. The resulting ions (Na+ and Cl-) attract electrostatically.
Question 2: Draw the Lewis structure for HCN. How many electrons total?
Answer: H-C triple bond N, with a lone pair on N
Total electrons: H(1) + C(4) + N(5) = 10 electrons
Question 3: What is the molecular geometry of H2O?
Answer: Bent
Oxygen has 2 bonding pairs and 2 lone pairs, giving a tetrahedral electron geometry but bent molecular geometry (approximately 104.5 degrees).
Question 4: Is BCl3 polar or nonpolar? Explain.
Answer: Nonpolar
BCl3 has trigonal planar geometry (symmetric). Although B-Cl bonds are polar, the three bond dipoles cancel out due to the symmetric arrangement.
Question 5: Why does sugar (C6H12O6) dissolve in water?
Answer: Sugar is polar (has many O-H groups that can hydrogen bond with water). Like dissolves like - polar sugar dissolves in polar water.
Question 6: Which has stronger intermolecular forces: CH4 or H2O? Explain.
Answer: H2O has stronger intermolecular forces.
H2O has hydrogen bonding (very strong IMF). CH4 only has weak London dispersion forces because it's nonpolar.
Question 7: What is the geometry of CO2?
Answer: Linear
Carbon has 2 double bonds and 0 lone pairs. The 2 bonding regions arrange linearly (180 degrees).
Question 8: Explain why ionic compounds have high melting points.
Answer: Ionic compounds have strong electrostatic attractions between oppositely charged ions in a crystal lattice. Breaking these attractions requires a large amount of energy, resulting in high melting points.
Question 9: Draw the Lewis structure for PH3 and determine if it's polar or nonpolar.
Answer: P with 3 single bonds to H and 1 lone pair. Polar molecule.
The geometry is trigonal pyramidal (like NH3), which is asymmetric. The bond dipoles don't cancel, making PH3 polar.
Question 10: A substance has a low melting point, does not conduct electricity, and does not dissolve in water. What type of substance is it most likely?
Answer: A nonpolar covalent (molecular) compound
Low melting point = weak intermolecular forces (covalent). No conductivity = no ions or free electrons. Insoluble in water = nonpolar (doesn't mix with polar water).
Self-Assessment
Count your correct answers and use the scoring guide to evaluate your mastery.
Review Recommendations
- Missed questions 1, 8: Review ionic bonding
- Missed questions 2, 9: Review Lewis structures
- Missed questions 3, 7: Review molecular geometry
- Missed questions 4, 5, 6, 10: Review polarity and properties
Next Steps
- Scored 9-10: Move on to Chemical Reactions
- Scored 7-8: Review missed topics, then continue
- Scored 5-6: Revisit Guided Practice and Common Mistakes
- Below 5: Work through the entire unit again