BENTUK MOLEKUL

Summary

The video introduces molecular shape and a shortcut for predicting it based on electron-pair domains around a central atom. These domains repel one another, and their arrangement determines a molecule’s shape.

Method

1. Identify the central atom, usually the atom connected to the others.
2. Find the total electron-pair count around it, called BK in the lesson. The presenter’s shortcut uses the central atom’s valence electrons, contributions from attached atoms, and any ionic charge, then divides by two.
   • A positive charge means electrons are removed; a negative charge means electrons are added.
   • The contribution assigned to attached atoms depends on the shortcut being used.
3. Find X, the number of atoms bonded to the central atom. In the examples, this is calculated as the total number of atoms minus one.

4. Find E, the number of lone pairs on the central atom: E = BK − X

5. Write the arrangement as AXₘEₙ:

   • A = central atom
   • X = bonded atoms
   • E = lone pairs
6. Use the AXₘEₙ pattern to name the molecular shape. Lone pairs affect the resulting shape because electron pairs repel one another.

Examples

• CH₄: AX₄; tetrahedral
• H₂O: AX₂E₂; bent/V-shaped
• CO₂: AX₂; linear
• NH₄⁺: AX₄; tetrahedral
• NH₂⁻: AX₂E₂; bent/V-shaped

Practice Questions

The presenter asks viewers to determine the molecular shape and its name for:

• PCl₅
• SF₆
• SO₄²⁻
• NH₃

The subtitles do not provide the solutions.

Speakers and Sources

• Presenter: Udin, associated with the KIM UD channel
• No other speakers or external sources are clearly featured.