2.4.2—Bonding triangle

The bonding triangle is a model for mixed ionic, covalent and metallic character. Its horizontal coordinate uses average electronegativity and its vertical coordinate uses electronegativity difference.

Calculate the two coordinates from the supplied electronegativities, place the substance, then check whether the predicted properties fit the indicated bonding contribution. The triangle is a qualitative model, not a requirement to memorise percentage boundaries.

For NaCl, using χ(Na)=0.9 and χ(Cl)=3.2 gives average χ = (0.9+3.2)/2 = 2.05 and Δχ = 3.2−0.9 = 2.3. The large difference places it near the ionic apex; that placement is consistent with a high-melting lattice and conduction only when ions can move.

Use the coordinates to compare materials rather than treating labels as absolute. A small Δχ can still sit at different average electronegativities, so metallic versus covalent character depends on both axes. Test the interpretation against conductivity, melting behaviour and mechanical response.