AP Chemistry Questions on Lewis Structures and Bonding

🧪 Quick Study Guide

• ⚛️ Lewis Structures: Represent valence electrons as dots or lines to show bonding in molecules. Follow the octet rule (usually!).
• 🔗 Covalent Bonds: Formed by sharing electrons between atoms. Single, double, and triple bonds exist.
• ⚡ Ionic Bonds: Formed by the transfer of electrons between atoms, resulting in ions.
• 📐 VSEPR Theory: Predicts molecular geometry based on minimizing electron pair repulsion. Common shapes: linear, trigonal planar, tetrahedral, bent, trigonal pyramidal.
• 📈 Bond Order: Number of bonds between two atoms. Higher bond order means shorter and stronger bond.
• polar bonds and molecular polarity: $ \Delta EN > 0.4 $ but molecular geometry matters!
• 💡 Formal Charge:** Helps determine the most stable Lewis structure. Calculated as: Valence electrons - Non-bonding electrons - (1/2 Bonding electrons).

Practice Quiz

1. Which of the following molecules has a linear geometry according to VSEPR theory?
   1. $H_2O$
   2. $NH_3$
   3. $CO_2$
   4. $CH_4$
2. What is the bond order of $N_2$?
   1. 1
   2. 2
   3. 3
   4. 4
3. Which of the following compounds contains ionic bonds?
   1. $CO_2$
   2. $H_2O$
   3. $NaCl$
   4. $CH_4$
4. What is the formal charge on the central atom in $SO_2$ (assuming each oxygen is bonded to the sulfur)?
   1. -1
   2. 0
   3. +1
   4. +2
5. Which of the following molecules is nonpolar, even though it contains polar bonds?
   1. $H_2O$
   2. $NH_3$
   3. $CO_2$
   4. $SO_2$
6. Which of the following molecules violates the octet rule?
   1. $H_2O$
   2. $BF_3$
   3. $NH_3$
   4. $CH_4$
7. How many sigma ($\sigma$) and pi ($\pi$) bonds are in a molecule of $C_2H_2$?
   1. 2 $\sigma$ and 2 $\pi$
   2. 3 $\sigma$ and 1 $\pi$
   3. 3 $\sigma$ and 2 $\pi$
   4. 2 $\sigma$ and 3 $\pi$