Results 1–9 of 9 for trigonal pyramidal
Trigonal pyramidal is a molecular shape that results when there are three bonds and one lone pair on the central atom in the molecule. Molecules with an tetrahedral electron pair geometries have sp3 hybridization at the central atom. Ammonia (NH3) is a trigonal pyramidal molecule.
Square pyramidal is a molecular shape that results when there are five bonds and one lone pair on the central atom in the molecule. Bromine pentafluoride (BrF5) has the geometry of a square pyramid, with fluorine atoms occupying five vertices, one of which is above the plane of the other four. This molecule is made up of six equally spaced sp3d2 (or d2sp3) hybrid orbitals arranged at 90° angles. The shape of the orbitals is octahedral. Because of the high symmetry of the octahedral arrangement, all six positions are equivalent, so it does not matter in which position in the drawing we put the lone pair. The remaining four atoms connected to the central atom give the molecule a square planar shape.
Trigonal bipyramidal (trigonal bipyramidal shape) is a molecular geometry that results when there are five bonds and no lone pairs on the central atom in the molecule. Three of the bonds are arranged along the atom’s equator, with 120° angles between them; the other two are placed at the atom’s axis. Axial bonds are at right angles to the equatorial bonds. Molecules with an trigonal bipyramidal electron pair geometries have sp3d (or dsp3) hybridization at the central atom. The PCl5 molecule has a trigonal bipyramidal molecular geometry.
Trigonal planar is a molecular shape that results when there are three bonds and no lone pairs around the central atom in the molecule. The pairs are arranged along the central atom’s equator, with 120° angles between them. Molecules with an trigonal planar electron pair geometries have sp2d hybridization at the central atom. The carbonate ion (CO32-) has a trigonal planar geometry.
Crystal system is a method of classifying crystalline substances on the basis of their unit cell. There are seven unique crystal systems. The simplest and most symmetric, the cubic (or isometric) system, has the symmetry of a cube. The other six systems, in order of decreasing symmetry, are hexagonal, tetragonal, rhombohedral (also known as trigonal), orthorhombic, monoclinic and triclinic.
Crystal system
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Unit-cell
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Conditions on unit-cell edges and angles |
cubic |
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a=b=c α=β=γ=90° |
hexagonal |
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a≠c α=γ=90° β=120° |
tetragonal |
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a=b≠c α=β=γ=90° |
rhombohedral |
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a=b=c α=β=γ≠90° |
orthorhombic |
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a≠b≠c α=β=γ=90° |
monoclinic |
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a≠b≠c α=γ=90°≠β |
triclinic |
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a≠b≠c α≠β≠γ≠90° |
Planary structure of molecule is a structure of molecule in which all atoms in the molecule lie in the same plane.
Rhombohedral crystal system is also known as the trigonal system. The crystallographic axes used in this system are of equal length. None of the axes are perpendicular to any other axis.
a = b = c
α= β = γ ≠ 90°
Rhombohedral (or trigonal) lattice has one lattice point at the each corner of the unit cell. It has unit cell vectors a=b=c and interaxial angles α=β=γ≠90°.
T-shape is a molecular geometry that results when there are 3 bonds and 2 lone pairs around the central atom in the molecule. The atoms bonded to the central atom lie at the ends of a T with 90° angles between them. Molecules with an trigonal bipyramidal electron pair geometries have sp3d (or dsp3) hybridization at the central atom. ICl3 has a T-shaped molecular geometry.
Generalic, Eni. "Trigonal pyramidal." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. 5 Apr. 2025. <https://glossary.periodni.com>.
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