Tetrahedral geometry is the molecular shape predicted by VSEPR theory when a central atom has four bonding pairs and zero lone pairs, placing the four bonded atoms at 109.5° angles to minimize electron-pair repulsion (AP Chem Topic 2.7).
Tetrahedral geometry is what you get when four electron domains around a central atom all hold bonded atoms. VSEPR theory (EK 2.7.A.1) says electron pairs repel each other through Coulombic repulsion, so they spread out as far apart as possible. For four domains, the farthest-apart arrangement in 3D space is a tetrahedron, with bond angles of 109.5°. Methane (CH₄) is the classic example.
The key skill is starting from the Lewis diagram. Count the electron domains on the central atom (bonding pairs plus lone pairs). Four domains with four bonds and no lone pairs gives tetrahedral. Swap one bond for a lone pair and the molecular geometry becomes trigonal pyramidal; swap two and it becomes bent. All three shapes share the same underlying tetrahedral electron geometry, which is why their bond angles all hover near (but slightly below) 109.5°. The lone pairs squeeze the bonding pairs closer together.
Tetrahedral geometry lives in Topic 2.7 (VSEPR and Bond Hybridization) in Unit 2 and supports learning objective 2.7.A, which asks you to use Lewis diagrams and VSEPR together to explain a molecule's structural and electron properties. EK 2.7.A.2 lists tetrahedral by name as one of the geometries you have to predict, along with its bond angles. It's also the gateway to two bigger ideas. First, four electron domains means sp3 hybridization, so geometry and hybridization are really one question asked two ways. Second, a molecule's shape determines whether its bond dipoles cancel, which decides molecular polarity and, downstream in Unit 3, which intermolecular forces it has. Getting tetrahedral right is the foundation for all of that.
Keep studying AP® Chemistry Unit 2
Lone pairs and trigonal pyramidal geometry (Unit 2)
Tetrahedral, trigonal pyramidal, and bent are siblings. They all come from four electron domains, but lone pairs replace bonded atoms one at a time. NH₃ has a tetrahedral electron arrangement, but because one domain is a lone pair, its molecular geometry is trigonal pyramidal with angles slightly under 109.5°.
sp3 hybridization (Unit 2)
Four electron domains means the central atom mixes one s and three p orbitals into four sp3 hybrid orbitals. If a question tells you a molecule is tetrahedral, it's also telling you the central atom is sp3, and vice versa. Same answer, two vocabularies.
Molecular polarity and dipole moment (Unit 2)
A perfectly symmetric tetrahedral molecule like CCl₄ is nonpolar even though every C–Cl bond is polar, because the four bond dipoles cancel. Replace one Cl with H (CHCl₃) and the symmetry breaks, giving a net dipole moment. Shape, not just bond polarity, decides molecular polarity.
sp2 hybridization and geometry changes (Unit 2)
When a trigonal planar (sp2) central atom gains a fourth bond, it shifts to sp3 and tetrahedral geometry, and the bond angles compress from 120° to 109.5°. AP questions love testing this before-and-after change because it checks VSEPR and hybridization in one shot.
Tetrahedral geometry shows up mostly in multiple-choice questions that hand you a Lewis structure (or describe one) and ask for the molecular geometry, the hybridization, or both at once. A typical stem describes a central atom bonded to four atoms with no lone pairs, or asks what happens to geometry and hybridization when a fourth atom bonds to a trigonal planar center (answer: sp2 to sp3, trigonal planar to tetrahedral, 120° to 109.5°). You also need to spot the trap where four electron domains do NOT mean tetrahedral molecular geometry because one domain is a lone pair, like nitrogen in NH₃, which is sp3 but trigonal pyramidal. No released FRQ has used the term as the headline, but geometry predictions regularly appear inside larger FRQs, where you draw a Lewis structure and then justify a bond angle or polarity claim using VSEPR. Always justify with electron-pair repulsion, not just memorized shapes.
Both come from four electron domains, so they look identical on a domain count. The difference is what fills the domains. Tetrahedral means four bonded atoms and zero lone pairs (CH₄, 109.5° angles). Trigonal pyramidal means three bonded atoms and one lone pair (NH₃, angles slightly less than 109.5° because the lone pair repels harder). If you say NH₃ is tetrahedral on an FRQ, you're describing its electron geometry, not its molecular geometry, and you'll lose the point.
Tetrahedral geometry occurs when a central atom has four bonding pairs and no lone pairs, producing 109.5° bond angles.
VSEPR theory predicts this shape because Coulombic repulsion pushes the four electron pairs as far apart as possible in 3D space (EK 2.7.A.1).
Four electron domains always means sp3 hybridization, so tetrahedral and sp3 go together every time.
If lone pairs replace bonding pairs, the molecular geometry changes to trigonal pyramidal (one lone pair) or bent (two lone pairs), with bond angles slightly below 109.5°.
A symmetric tetrahedral molecule like CCl₄ is nonpolar because its bond dipoles cancel, but breaking the symmetry (CHCl₃) creates a net dipole.
Always start from the Lewis diagram and count electron domains; the AP exam requires using Lewis structures and VSEPR together (LO 2.7.A).
It's the molecular shape formed when a central atom has four bonding pairs and no lone pairs, with the bonded atoms spread to 109.5° angles. VSEPR theory predicts it because four electron pairs repel each other into the farthest-apart 3D arrangement, a tetrahedron. CH₄ is the standard example.
No, not as a molecular geometry. NH₃ has four electron domains, so its electron geometry is tetrahedral, but one domain is a lone pair, making the molecular geometry trigonal pyramidal with angles around 107°. On the AP exam, specify which geometry you mean.
Tetrahedral has four bonded atoms and zero lone pairs (CH₄, 109.5°). Trigonal pyramidal has three bonded atoms and one lone pair (NH₃, slightly under 109.5° because the lone pair repels more strongly). Both share a tetrahedral electron-domain arrangement.
Because molecules are 3D, not flat. Four electron pairs at 90° would describe a flat square, but spreading into three dimensions lets them get even farther apart at 109.5°, which minimizes Coulombic repulsion per VSEPR theory.
No. It's nonpolar only when all four attached atoms are identical, so the bond dipoles cancel (CCl₄). If even one atom differs, like CHCl₃, the molecule has a net dipole moment and is polar. Symmetry plus bond polarity together determine molecular polarity.
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