Linear, trigonal planar, tetrahedral: electron domain geometries explained

📚 Electron Domain Geometries Explained

Electron domain geometry focuses on the arrangement of all electron domains (bonds and lone pairs) around a central atom. It's the foundation for understanding molecular shapes.

🧪 Linear Geometry

• ⚛️ A molecule is linear when the central atom is bonded to two other atoms, and there are no lone pairs on the central atom.
• 📐 The bond angle is 180°.
• 📝 Example: $CO_2$. Carbon is double-bonded to two oxygen atoms ($O=C=O$).

📐 Trigonal Planar Geometry

• ⚛️ A molecule exhibits trigonal planar geometry when the central atom is bonded to three other atoms, and there are no lone pairs on the central atom.
• 📐 The bond angles are 120°.
• 📝 Example: $BF_3$. Boron is bonded to three fluorine atoms.

SixElectron Geometry

• ⚛️ A molecule exhibits tetrahedral geometry when the central atom is bonded to four other atoms, and there are no lone pairs on the central atom.
• 📐 The bond angles are approximately 109.5°.
• 📝 Example: $CH_4$. Carbon is bonded to four hydrogen atoms.

💡 Key Differences & Summary

The key difference lies in the number of atoms bonded to the central atom and the presence/absence of lone pairs. Here's a table summarizing the geometries:

📝 Practice Quiz

Identify the electron domain geometry of the central atom in each of the following molecules:

1. $BeCl_2$
2. $SO_3$
3. $CCl_4$
4. $H_2O$ (Hint: consider lone pairs on oxygen)
5. $BH_3$

Answers: 1. Linear, 2. Trigonal Planar, 3. Tetrahedral, 4. Tetrahedral (bent molecular shape), 5. Trigonal Planar