Lone pair-lone pair repulsion exceeds lone pair-bond pair, which exceeds bond pair-bond pair.
Practise Bonding & Molecular Structure All Bonding & Molecular Structure topics
The ranking of electron-pair repulsions is a central part of VSEPR theory. Lone pair-lone pair repulsion is the strongest, because lone pairs are held by a single nucleus and occupy more space. Lone pair-bonding pair repulsion is intermediate, and bonding pair-bonding pair repulsion is the weakest, since bonding electron density is shared between two nuclei and drawn closer. Multiple bonds count as more repulsive than single bonds because they occupy more space. This ranking predicts where lone pairs sit and how bond angles are distorted.
Key ideas: Apply the ranking as lone pair-lone pair greater than lone pair-bond pair greater than bond pair-bond pair. Further refinement: bond pairs to electronegative atoms take up less space, and double bonds take up more than single bonds. In five-domain cases, lone pairs choose equatorial sites since only two 90 degree contacts occur there compared with three axial.
Common mistakes and connections: Typical errors are putting lone pairs in axial sites, thinking that all 90 degree interactions are equal in importance, and ignoring that repulsions at 90 degrees matter most while 120 degrees and above are minor. In octahedral AX4E2 the two lone pairs go opposite, at 180 degrees. Links to molecular geometry, bond angle trends and polarity.
As lone pairs are added, repulsion of lp-bp exceeds bp-bp and bond angles shrink from 109.5 to 104.5 degrees, confirming the ranking. The interactive lesson shows this as a live animation or chart.
In ClF3 the two lone pairs sit in equatorial positions, 120 degrees apart, where they experience the fewest strong repulsions.
Lone pair-lone pair repulsion exceeds lone pair-bond pair, which exceeds bond pair-bond pair.
Electron-Pair Repulsion Ranking is a advanced topic in Bonding & Molecular Structure. It builds on beginner and intermediate topics, so review those first if needed.
Study these earlier topics in Bonding & Molecular Structure first: Banana Bonds, Van der Waals Radius, Covalent Radius.
The next topics in Bonding & Molecular Structure are Bent's Rule.
Yes. The interactive lesson includes a self-check question on Electron-Pair Repulsion Ranking, and the Bonding & Molecular Structure quiz draws on every topic in this area.
Electron-Pair Repulsion Ranking is topic 103 of 104 in Bonding & Molecular Structure.