A.1 Bonding triangle diagrams (SL)

Bonding Triangle Diagrams

A bonding triangle diagram helps identify the type of bonding in a substance using the atoms’ electronegativity values. The diagram uses:

• Y-axis: Difference in electronegativity between the two atoms
• X-axis: Average electronegativity of the two atoms

How to Use the Diagram

1. Find the electronegativity values of the two atoms.
2. Calculate their electronegativity difference.
3. Calculate their average electronegativity by adding the two values and dividing by two.
4. Plot the result on the bonding triangle:
   • Plot the difference on the y-axis.
   • Plot the average on the x-axis.
5. Identify the bonding type from the region containing the point.

Examples

• Chlorine (Cl₂): Difference = 0; average = 3.2 → covalent
• Cesium fluoride (CsF): Difference = 3.2; average = 2.4 → ionic
• Magnesium (Mg): Difference = 0; average = 1.3 → metallic
• Hydrogen chloride (HCl): Difference = 1.0; average = 2.7 → polar covalent

Percentage Ionic Character

The percentage ionic character is calculated as:

Percentage ionic character = (electronegativity difference ÷ 3.2) × 100

For hydrogen chloride, the electronegativity difference is 1.0, giving approximately 31% ionic character. The bond is therefore described as 31% ionic and 69% covalent.

Speaker

Mike Sugiyama Jones (MSJ Chem) is the narrator and presenter.