Trigonal Planar Geometry Molecular Model

SKU: 68823W

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The Indigo® 68823W VSEPR model kit builds both trigonal planar AX₃ and bent AX₂E models simultaneously so tutors can show how a single lone pair distorts 120° geometry in BF₃, SO₂, and CH₂O side by side.

Trigonal planar geometry introduces students to electron pairs and bonding atoms sharing a single plane. The effects of replacing just one bonding atom with a lone pair is immediately clear. The Indigo® 68823W VSEPR model kit includes two trigonal planar central atoms for building AX₃ and AX₂E configurations simultaneously for comparison. A symmetric BF₃ or SO₃ model juxtaposed with a bent SO₂ model makes the lone pair distortion obvious. Tutors can show the transition from 120° symmetry to the compressed geometry of AX₂E, making electron domain repulsion a tangible entity. Formaldehyde (CH₂O) adds a further nuance. Its trigonal planar carbon shows how double bonds count as single electron domains in VSEPR theory, connecting molecular geometry directly to bonding theory and reactivity. (Note that an actual bond needs extra parts as seen in this representation)

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Details

Summary of Trigonal Shapes

Each of the two AX₃ configurations produces distinct bond angles whose differences, though small, connect directly to molecular polarity and reactivity. The fully bonded AX₃ arrangement achieves exact trigonal planar symmetry with all bond angles at exactly 120°. In BF₃ every fluorine atom experiences identical repulsion forces, the molecule lies completely flat, and the absence of a dipole moment makes it a useful electrophile in Lewis acid-base chemistry.

SO₃ shares the same geometry and similarly has no net dipole moment despite its polar bonds. Replacing one bonding atom with a lone pair gives the bent geometry of AX₂E. In SO₂ the lone pair compresses the O-S-O bond angle from 120° to approximately 119°. This is a small distortion numerically but has significant consequences. Unlike SO₃, sulfur dioxide has a measurable dipole moment, behaves very differently in solution, and is central to discussions of atmospheric chemistry and acid rain. The model makes the source of that asymmetry immediately visible.

Formaldehyde (CH₂O) offers a third perspective on trigonal planar geometry. The central carbon forms a double bond to oxygen and two single bonds to hydrogen, and VSEPR theory treats the double bond as a single electron domain. This trigonal planar molecule has bond angles close to 120°, connecting molecular geometry directly to the concept of sp² hybridization and opening discussion of how multiple bonds influence shape.

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Parts

P/N	Description	QTY
68186-20	Wobbly bond, 20mm, each	50
68216C	Atom, Orbit, H "a", white, 1 prong	20
68221C	Atom, Orbit, Cl "a", green, 1 prong	30
68225C	Atom, Orbit, C "b", 180 degree, black	1
68241C	Atom, Orbit, C "j", planar: 120-120-120, black	2
68244C	Atom, Orbit, C "k", tetrahedral, black	3
68258C	Atom, Orbit "l", octahedral, grey	5
68259C	Atom, Orbit, C "m", trigonal bipyramidal, black	4
68416C	Orbital for showing lone electron pair, white, Orbit style	10
68417C	Orbital for showing lone electron pair, black, Orbit style	10

Specifications

The parts listed on this page are for the entire kit, not the molecules(s) shown. You can augment this geometry with additional pieces listed on the Orbit Components page.

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Trigonal Planar Geometry Molecular Model