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In a tetrahedral molecular geometry, a central atom is located at the center with four substituents that are located at the corners of a tetrahedron.The bond angles are arccos(− 1 / 3 ) = 109.4712206...° ≈ 109.5° when all four substituents are the same, as in methane (CH 4) [1] [2] as well as its heavier analogues.
Most commonly, four bonds to a central atom result in tetrahedral or, less commonly, square planar geometry. The seesaw geometry occurs when a molecule has a steric number of 5, with the central atom being bonded to 4 other atoms and 1 lone pair (AX 4 E 1 in AXE notation).
For example, methane (CH 4) is a tetrahedral molecule. Octahedral: Octa-signifies eight, and -hedral relates to a face of a solid, so "octahedral" means "having eight faces". The bond angle is 90 degrees. For example, sulfur hexafluoride (SF 6) is an octahedral molecule.
The methane molecule (CH 4) is tetrahedral because there are four pairs of electrons. The four hydrogen atoms are positioned at the vertices of a tetrahedron, and the bond angle is cos −1 (− 1 ⁄ 3) ≈ 109° 28′. [16] [17] This is referred to as an AX 4 type of molecule. As mentioned above, A represents the central atom and X represents ...
where: α and β are the two greatest valence angles of coordination center; θ = cos −1 (− 1 ⁄ 3) ≈ 109.5° is a tetrahedral angle. When τ 4 is close to 0 the geometry is similar to square planar, while if τ 4 is close to 1 then the geometry is similar to tetrahedral.
Tetrahedrane is a hypothetical platonic hydrocarbon with chemical formula C 4 H 4 and a tetrahedral structure. The molecule would be subject to considerable angle strain and has not been synthesized as of 2023. However, a number of derivatives have been prepared.
Notably, white phosphorus, the most stable allotrope of phosphorus, is tetrahedral with the molecular formula P 4. [7] Arsenic can also exist as a metastable tetrahedral allotrope, As 4, known as yellow arsenic. Furthermore, mixed tetrahedral pnictogen molecules have been synthesized, such as AsP 3 [8] and, more recently, (PbBi 3)-. [9]
All sp 3-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.