Distorted T Molecular Shape
A focused revision guide to the distorted T molecular shape, using ClF3 as the key example. This page explains why three bonding pairs and two lone pairs around a central atom give a T-shaped arrangement with bond angles close to 89°.
What Distorted T Means
A distorted T molecule has three atoms bonded to a central atom in a T-shaped arrangement. It is called distorted because the bond angles are slightly compressed by lone pair repulsion.
The key example for this page is ClF3. Chlorine is the central atom, three fluorine atoms are bonded to chlorine, and chlorine also has two lone pairs.
Key idea: three bonding pairs and two lone pairs around a central atom give a distorted T shape when the two lone pairs occupy equatorial positions in a trigonal bipyramidal electron-pair arrangement.
Why ClF3 Is Distorted T-Shaped
In ClF3, the central chlorine atom is surrounded by three Cl-F bonding pairs and two lone pairs. This gives five regions of negative charge around chlorine.
Five electron regions arrange themselves as a trigonal bipyramidal electron-pair arrangement to minimise repulsion. The two lone pairs occupy equatorial positions, where they are approximately 120° apart from each other.
The molecular shape only describes the positions of the atoms. Therefore, ClF3 is described as distorted T-shaped, even though its electron-pair arrangement is trigonal bipyramidal.
A distorted T species has three bonding regions and two lone pairs around the central atom. ClF3 is the standard example, with bond angles close to 89°.
Distorted T Shape of ClF3
In chlorine trifluoride, chlorine has three Cl-F bonding pairs and two lone pairs. The five electron regions arrange themselves as a trigonal bipyramidal electron-pair arrangement. The two lone pairs occupy equatorial positions, where they are approximately 120° apart, leaving two axial bonds and one equatorial bond to form a distorted T-shaped molecule.
Electron-Pair Arrangement vs Molecular Shape
The electron-pair arrangement in ClF3 is based on a trigonal bipyramidal arrangement because there are five electron regions around chlorine.
The molecular shape is different. Lone pairs are not counted as atoms when naming the shape, so the visible arrangement of the three fluorine atoms is distorted T-shaped.
Five electron regions
Three bonding pairs and two lone pairs arrange themselves as far apart as possible around chlorine.
Equatorial lone pairs
The two lone pairs occupy equatorial positions in the trigonal bipyramidal arrangement. This keeps the lone pairs approximately 120° apart and reduces lone pair-lone pair repulsion.
T-shaped bonded atoms
The remaining three bonding pairs form two axial bonds and one equatorial bond, producing a distorted T shape.
Distorted T Shape Examples
The distorted T shape is found when the central atom has three bonding pairs and two lone pairs. The common exam examples are usually interhalogen species.
| Species | Central atom | Electron regions | Shape | Typical exam angle |
|---|---|---|---|---|
| ClF3 | Cl | 3 bonding regions, 2 lone pairs | Distorted T | 89° |
| BrF3 | Br | 3 bonding regions, 2 lone pairs | Distorted T | 89° |
| IF3 | I | 3 bonding regions, 2 lone pairs | Distorted T | 89° |
| ICl3 | I | 3 bonding regions, 2 lone pairs | Distorted T | 89° |
| XeF2Cl– | Xe | 3 bonding regions, 2 lone pairs | Distorted T | 89° |
How to Explain Distorted T Shape in an Exam
A full exam explanation should connect the number of electron regions to electron-pair repulsion, then explain why the two lone pairs are equatorial and why the bonded atoms form a T shape.
1. Identify the central atom
For ClF3, the central atom is chlorine.
2. Count bonding pairs and lone pairs
Chlorine has three bonding pairs and two lone pairs around it.
3. Apply electron-pair repulsion
The five electron regions arrange themselves as far apart as possible. The two lone pairs occupy equatorial positions to reduce repulsion.
4. State the shape and angle
The three bonded atoms form a distorted T shape. The bond angles are close to 89° in the usual A Level exam table, with the straight angle close to 180°.
Exam answer model: ClF3 has three bonding pairs and two lone pairs around the central chlorine atom. The five electron regions arrange themselves as a trigonal bipyramidal electron-pair arrangement. The two lone pairs occupy equatorial positions to minimise repulsion. Therefore, ClF3 is distorted T-shaped, with bond angles close to 89°.
Common Exam Points
Do not call ClF3 trigonal bipyramidal
The electron-pair arrangement is trigonal bipyramidal, but the molecular shape is distorted T because the two lone pairs are not counted as atoms.
State the lone pairs are equatorial
The two lone pairs occupy equatorial positions. This gives fewer 90° lone pair interactions than placing a lone pair in an axial position.
Use 89° for the exam-table angle
The common A Level table value is approximately 89°. In more detailed explanations, the bp-bp angles are slightly less than 90° and slightly less than 180°.
Count around the central atom only
The shape is determined by the bonding pairs and lone pairs around the central atom, not by the total number of atoms in the species.
Check Your Understanding
Use these short activities to check the distorted T shape, ClF3, three bonding pairs, two lone pairs and the approximately 89° bond angle.
QuickSnap
The distorted T shape is produced when a central atom has three bonding pairs and two lone pairs. The lone pairs occupy equatorial positions in a trigonal bipyramidal electron-pair arrangement, leaving three bonded atoms in a T-shaped arrangement with bond angles close to 89°.
Memory line: 3 bonding pairs + 2 lone pairs = distorted T = about 89°.
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The shapes of some species are being compared.
Which species is not tetrahedral?
Explain this difference in terms of structure and bonding.
Distorted T FAQs
These questions target the points students most often lose marks on when explaining the distorted T molecular shape.
Why is ClF3 distorted T-shaped?
ClF3 is distorted T-shaped because chlorine has three bonding pairs and two lone pairs. The five electron regions arrange as trigonal bipyramidal, but the two lone pairs occupy equatorial positions, leaving two axial Cl-F bonds and one equatorial Cl-F bond.
What is the bond angle in a distorted T molecule?
The common A Level exam-table angle is about 89°. More detailed descriptions may state that the bond-pair to bond-pair angles are slightly less than 90° and close to 180°.
Is distorted T the same as trigonal bipyramidal?
No. Trigonal bipyramidal is the electron-pair arrangement for five regions of negative charge. Distorted T is the molecular shape after the two lone pairs are ignored when naming the shape.
Why do the lone pairs in ClF3 occupy equatorial positions?
The lone pairs occupy equatorial positions because this arrangement minimises repulsion. The two lone pairs are approximately 120° apart and avoid unnecessary 90° lone pair-lone pair interactions.
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