Tetrahedral Geometry Molecular Model

SKU: 68823W

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The Indigo® 68823W VSEPR Theory Model Kit can simultaneously build tetrahedral, trigonal pyramidal, and bent geometry so tutors can compare CH4, NH3, and H2O lone pair distortions side by side.

The tetrahedral shape is at the heart of VSEPR theory. Methane, ammonia, and water are three of the most important molecules in all of chemistry, and all three share the same underlying electron geometry while producing three distinctly different molecular shapes. The Indigo® 68823W VSEPR Theory Model Kit includes three tetrahedral central atoms to build AX4, AX3E, and AX2E2 configurations simultaneously. Students can see CH4, NH3, and H2O & their respective geometry distortions as each lone pair displaces a bonding atom. The two colors of lone pair paddles reinforce this further. In the bent geometry of H2O, the contrasting paddles make it clear both lone pairs are present. Their combined repulsion accounts for the H-O-H angle's being below the ideal 109.5°.

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Details

Summary of Tetrahedral Shapes

Each of the three AX4 configurations produces measurably distinct bond angles whose differences correlate with their physical and chemical properties. The fully bonded AX4 arrangement of CH4 shows exact tetrahedral symmetry with all bond angles at exactly 109.5°. Every hydrogen atom experiences identical repulsion forces, the molecule has no dipole moment, and methane serves as the simplest possible baseline for understanding how electron pair repulsion determines shape.

Replacing one bonding atom with a lone pair yields trigonal pyramidal geometry of NH3 (AX3E). The lone pair occupies more space than a bonding pair and compresses the three H-N-H bond angles from 109.5° to approximately 107°. This small distortion is nevertheless significant; ammonia has a measurable dipole moment, behaves as a nucleophile, and is central to acid-base chemistry. The model makes this asymmetry clearly visible in a way that a structural formula never quite does.

In the bent geometry of H2O (AX2E2), two lone pairs compress the H-O-H bond angle further still, to approximately 104.5°. The cumulative repulsion of two lone pairs produces a strongly polar molecule whose dipole moment underlies hydrogen bonding, surface tension, and the anomalous properties of water that make life possible.

Placing all three models side by side makes the progressive compression from 109.5° to 107° to 104.5° immediately intuitive as each lone pair changes the bond angle ~2-3°. Students can see and feel the difference. 

Related information or images
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Advanced VSEPR Theory Molecular Model Kit

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Trigonal Planar Geometry Molecular Model

Trigonal Planar

Trigonal Bipyramidal Geometry Molecular Model

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Octahedral Geometry Molecular Model

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VSEPR Theory Polarity/Dipole Models

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VSEPR Theory Distorted Lone Pair Geometries

Variations/Distorted Geometries

Acetylene Molecular Model + Orbitals

Unsaturated Hydrocarbons

Parts
P/NDescriptionQTY
68186-20Wobbly bond, 20mm, each50
68216CAtom, Orbit, H "a", white, 1 prong20
68221CAtom, Orbit, Cl "a", green, 1 prong30
68225CAtom, Orbit, C "b", 180 degree, black1
68241CAtom, Orbit, C "j", planar: 120-120-120, black2
68244CAtom, Orbit, C "k", tetrahedral, black3
68258CAtom, Orbit "l", octahedral, grey5
68259CAtom, Orbit, C "m", trigonal bipyramidal, black4
68416COrbital for showing lone electron pair, white, Orbit style10
68417COrbital for showing lone electron pair, black, Orbit style10
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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