Lewis Structures Summary

Writing Lewis Structures

• Objective: Draw Lewis structures depicting bonding in molecules and molecular ions.

• Procedure for Simple Molecules: Pair unpaired electrons on constituent atoms.

Steps for Complicated Molecules:

1. Count Valence Electrons:

• For cations, subtract electrons for each positive charge.

• For anions, add electrons for each negative charge.

• 2. Skeleton Structure:

• Arrange atoms with the least electronegative in the center.

• Connect with single bonds (one electron pair).

1. Distribute Remaining Electrons:

• Assign lone pairs on terminal atoms (except hydrogen) to complete octets.

1. Central Atom Electrons:

• Place remaining electrons on the central atom.

1. Multiple Bonds:

• Rearrange outer atoms' electrons to form multiple bonds with central atom for octets.

• Example 1: CCl4 (Carbon Tetrachloride):

  • Total valence electrons: 32.

  • Every chlorine atom completed with three lone pairs.

• Example 2: OF2 (Oxygen Difluoride):

  • Total valence electrons: 20.

  • Each fluorine has lone pairs to complete octets.

• Example 3: CHO2− (Formate Ion):

  • Total valence electrons: 18.

  • Complete the octet for oxygen using multiple bonding.