2.2.2—Bond types and strength

Bond	Shared pairs	Relative length and strength
Single	1	Longest and weakest of the three
Double	2	Shorter and stronger
Triple	3	Shortest and strongest

More shared electron pairs increase electron density between nuclei, so the bond becomes shorter and stronger.

For the same pair of atoms, increasing bond order generally shortens and strengthens the bond because more electron density lies between the nuclei. Use that comparison locally: bond enthalpy also depends on the atoms and molecular environment, so any triple bond is not automatically stronger than every unrelated single bond.

Representative question

[Maximum number: 1]

Compare, giving a reason, the length of the bond between the carbon atoms in ethyne with that in ethane, $\mathrm{C}_{2} \mathrm{H}_{6}$ .

Retrieve the covalent pathway: shared pairs and bond order lead to geometry, polarity and molecular polarity; structure determines network properties, IMF behaviour and chromatography; HL representations extend to resonance, formal charge, sigma/pi bonds and hybridization.

Check the representation first, then count domains, apply geometry, identify polarity or forces, and connect the structure to the requested property or HL bonding description.

2.2.2—Bond types and strength

Bond Types and Strength

Comparing Bond Strength

Assessment in practice

The Covalent Model Summary

Question 1