Octahedral geometry is the VSEPR shape formed when six bonding pairs surround a central atom with no lone pairs, placing atoms at the six vertices of an octahedron with all bond angles at 90°. SF₆ is the classic AP Chem example.
Octahedral geometry is what you get when a central atom has six electron domains and all six are bonding pairs. VSEPR theory (EK 2.7.A.1) says electron pairs repel each other through Coulombic repulsion and spread out as far as possible. With six domains, the farthest-apart arrangement puts atoms at the six corners of an octahedron, with every bond angle at exactly 90°.
Picture a plus sign with one atom poking straight up and one straight down. Four atoms sit in a square plane around the central atom, and two more sit above and below it. SF₆ is the textbook example, with sulfur using an expanded octet to bond six fluorines. Because all six positions are identical, a molecule like SF₆ with six identical atoms is perfectly symmetric, so the individual bond dipoles cancel and the molecule is nonpolar even though each S-F bond is polar.
Octahedral geometry lives in Topic 2.7 (VSEPR and Bond Hybridization) in Unit 2: Compound Structure and Properties. It directly supports learning objective 2.7.A, which asks you to use Lewis diagrams and VSEPR together to explain structural and electronic properties of molecules. The CED explicitly lists octahedral, square pyramidal, and square planar among the geometries you're responsible for (EK 2.7.A.2), so this is one of the named shapes the exam can ask about by name.
Octahedral also matters because it's the parent geometry for two derived shapes. Swap one bonding pair for a lone pair and you get square pyramidal. Swap two and you get square planar. If you know the octahedral framework, those two shapes come for free, and so do questions about whether the resulting molecule is polar.
Keep studying AP® Chemistry Unit 2
Lone pair effects on shape (Unit 2)
Lone pairs occupy positions in the octahedron just like bonds do, but you only name the shape by where the atoms are. One lone pair gives square pyramidal (like BrF₅), and two lone pairs sit opposite each other to give square planar (like XeF₄). Octahedral is the starting template for both.
Molecular polarity (Unit 2)
A perfectly octahedral molecule with six identical outer atoms, like SF₆, is nonpolar because the bond dipoles cancel in every direction. Replace one atom or add lone pairs and the symmetry breaks, which can leave a net dipole moment. Geometry is step one of every polarity question.
sp3 hybridization and its limits (Unit 2)
AP Chem only assesses sp, sp2, and sp3 hybridization, which cover up to four electron domains. Octahedral centers have six domains, so the exam won't ask you to name the hybridization of SF₆. You just need to predict the shape and angles from VSEPR.
Lewis diagrams and expanded octets (Unit 2)
You can't get to octahedral without first drawing a Lewis structure that puts more than eight electrons on the central atom. Only elements in period 3 and below (like S, Br, Xe) can do this, which is why octahedral centers are never carbon, nitrogen, or oxygen.
Octahedral geometry shows up most often in multiple-choice questions that give you a molecule like SF₆ and ask you to name the geometry, or that describe an electron arrangement and ask you to identify the shape. Watch for the classic trap question that gives you six electron domains where one or two are lone pairs; the electron geometry is octahedral, but the molecular geometry is square pyramidal or square planar. On free-response questions, geometry usually appears as part of a chain. You draw the Lewis structure, name or sketch the geometry, state the bond angles (90° for octahedral), and then use the shape to justify whether the molecule is polar or nonpolar. The justification step is where points are won or lost, so always connect the symmetry of the shape to whether bond dipoles cancel.
Both come from six electron domains, so they're easy to mix up. Octahedral means all six domains are bonding pairs, with atoms at all six vertices. Square planar means two of those domains are lone pairs sitting opposite each other (top and bottom), leaving four atoms in a flat square. XeF₄ is square planar, not octahedral, even though its electron geometry is octahedral. The rule that saves you is to name the molecular geometry by atom positions only, never by lone pairs.
Octahedral geometry happens when a central atom has six bonding pairs and zero lone pairs, putting atoms at the six corners of an octahedron.
All bond angles in an octahedral molecule are 90°, which makes it one of the easiest geometries to remember.
SF₆ is the go-to example, and it's nonpolar because its six identical bond dipoles cancel by symmetry.
One lone pair turns octahedral into square pyramidal, and two lone pairs (opposite each other) turn it into square planar.
Octahedral centers require an expanded octet, so the central atom must be from period 3 or below, never carbon, nitrogen, or oxygen.
The AP exam won't ask for the hybridization of an octahedral center, since only sp, sp2, and sp3 are assessed.
It's the VSEPR shape for a central atom with six bonding pairs and no lone pairs, with atoms at the six vertices of an octahedron and all bond angles at 90°. SF₆ is the standard example, and it's part of the geometry list in EK 2.7.A.2.
XeF₄ is square planar. Its electron geometry is octahedral because xenon has six electron domains, but two of them are lone pairs, so only four atoms are visible in a flat square. Molecular geometry is named by atom positions, not electron domains.
All bond angles are 90°. Each of the four equatorial atoms sits 90° from its neighbors and 90° from the two axial atoms above and below.
No. The AP Chem CED only assesses sp, sp2, and sp3 hybridization, which cover up to four electron domains. For six-domain molecules like SF₆, you only need VSEPR to predict the shape, angles, and polarity.
Octahedral has six electron domains with all 90° angles, while trigonal bipyramidal has five domains with a mix of 90° and 120° angles. If a question describes three atoms at 120° in a plane plus two on a vertical axis, that's trigonal bipyramidal, not octahedral.
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