page_title: Tetrahedron
section_title: Chemistry
hierarchical_section_title: Tetrahedron / Applications / Chemistry
context_page_description: In geometry, a tetrahedron, also known as a triangular pyramid, is a polyhedron composed of four triangular faces, six straight edges, and four vertex corners. The tetrahedron is the simplest of all the ordinary convex polyhedra and the only one that has fewer than 5 faces.
  The tetrahedron is the three-dimensional case of the more general concept of a Euclidean simplex, and may thus also be called a 3-simplex.
  The tetrahedron is one kind of pyramid, which is a polyhedron with a flat polygon base and triangular faces connecting the base to a common point. In the case of a tetrahedron the base is a triangle, so a tetrahedron is also known as a "triangular pyramid".
  Like all convex polyhedra, a tetrahedron can be folded from a single sheet of paper. It has two such nets.
  For any tetrahedron there exists a sphere on which all four vertices lie, and another sphere tangent to the tetrahedron's faces.
context_section_description: The tetrahedron shape is seen in nature in covalently bonded molecules. All sp³-hybridized atoms are surrounded by atoms (or lone electron pairs) at the four corners of a tetrahedron. For instance in a methane molecule (CH
  ₄) or an ammonium ion (NH⁺
  ₄), four hydrogen atoms surround a central carbon or nitrogen atom with tetrahedral symmetry. For this reason, one of the leading journals in organic chemistry is called Tetrahedron. The central angle between any two vertices of a perfect tetrahedron is arccos(−), or approximately 109.47°.
  Water, H
  ₂O, also has a tetrahedral structure, with two hydrogen atoms and two lone pairs of electrons around the central oxygen atoms. Its tetrahedral symmetry is not perfect, however, because the lone pairs repel more than the single O–H bonds.
  Quaternary phase diagrams in chemistry are represented graphically as tetrahedra.
  However, quaternary phase diagrams in communication engineering are represented graphically on a two-dimensional plane.
caption: The ammonium ion is tetrahedral
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