| Trigonal bipyramidal molecular geometry | |
|---|---|
 |
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| Examples | PF5 |
| Point group | D3h |
| Steric number | 5 |
| Coordination number | 5 |
| Bond angle(s) | 90°, 120°, 180° |
| μ (Polarity) | 0 |
In chemistry a trigonal bipyramid formation is a molecular geometry with one atom at the center and 5 more atoms at the corners of a triangular dipyramid. This is one of the few cases where bond angles surrounding an atom are not identical (see also pentagonal dipyramid), which is simply because there is no geometrical arrangement which can result in five equally sized bond angles in three dimensions.
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Behavior [link]
Isomers with a trigonal bipyramidal geometry are able to interconvert through a process known as Berry pseudorotation. Pseudorotation is similar in concept to the movement of a conformational diastereomer, though no full revolutions are completed. In the process of pseudorotation, two equatorial ligands (both of which have a shorter bond length than the third) "shift" toward the molecule's axis, while the axial ligands simultaneously "shift" toward the equator, creating a constant cyclical movement. Pseudorotation is particularly notable in simple molecules such as PF5.
Examples [link]
Phosphorus pentachloride is a molecule with a trigonal bipyramidal geometry. The phosphorus atom shares a plane with three chlorine atoms which are at 120 degrees angles to each other (equatorial positions), with two more chlorine atoms above and below the plane (apical or axial positions). The triiodide ion is also based upon a trigonal bipyramid, but with the equatorial positions filled with lone pairs of electrons. In phosphorus compounds with mixed substituents apicophilicity is observed.
See also [link]
External links [link]
- Chem Chemistry, Structures, and 3D Molecules
- Indiana University Molecular Structure Center
- Point Group Symmetry Interactive Examples
- Molecular Modeling
- Animated Trigonal Planar Visual
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https://wn.com/Trigonal_bipyramidal_molecular_geometry
Cell membrane
The cell membrane (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells. The basic function of the cell membrane is to protect the cell from its surroundings. It consists of the phospholipid bilayer with embedded proteins. Cell membranes are involved in a variety of cellular processes such as cell adhesion, ion conductivity and cell signalling and serve as the attachment surface for several extracellular structures, including the cell wall, glycocalyx, and intracellular cytoskeleton. Cell membranes can be artificially reassembled.
Function
The cell membrane (or plasma membrane or plasmalemma) surrounds the cytoplasm of living cells, physically separating the intracellular components from the extracellular environment. Fungi, bacteria and plants also have a cell wall in addition, which provides a mechanical support to the cell and precludes the passage of larger molecules. The cell membrane also plays a role in anchoring the cytoskeleton to provide shape to the cell, and in attaching to the extracellular matrix and other cells to help group cells together to form tissues.
Glossary of dentistry
This is a list of commonly used terms of location and direction in dentistry. This set of terms provides orientation within the oral cavity, much as anatomical terms of location provide orientation throughout the body.
Combining of terms
Most of the principal terms can be combined using their corresponding combining forms (such as mesio- for mesial and disto- for distal). They provide names for directions (vectors) and axes; for example, the coronoapical axis is the long axis of a tooth. Such combining yields terms such as those in the following list. The abbreviations should be used only in restricted contexts, where they are explicitly defined and help avoid extensive repetition (for example, a journal article that uses the term "mesiodistal" dozens of times might use the abbreviation "MD"). The abbreviations are ambiguous: (1) they are not specific to these terms; (2) they are not even one-to-one specific within this list; and (3) some of the combined terms are little used, and the abbreviations of the latter are even less used. Therefore, spelling out is best.
Anatomical terms of location
Standard anatomical terms of location deal unambiguously with the anatomy of animals, including humans.
All vertebrates (including humans) have the same basic body plan — they are bilaterally symmetrical. That is, they have mirror-image left and right halves if divided down the centre. For these reasons, the basic directional terms can be considered to be those used in vertebrates. By extension, the same terms are used for many other (invertebrate) organisms as well.
While these terms are standardized within specific fields of biology, there are unavoidable, sometimes dramatic, differences between some disciplines. For example, differences in terminology remain a problem that, to some extent, still separates the terminology of human anatomy from that used in the study of various other zoological categories.
Introduction
Standardized anatomical and zoological terms of location have been developed, usually based on Latin and Greek words, to enable all biological and medical scientists to precisely delineate and communicate information about animal bodies and their component organs, even though the meaning of some of the terms often is context-sensitive.
Etymology of chemistry
In the history of science, the etymology of the word chemistry is debatable. It is agreed that the word derives from the word alchemy, which is a European one, derived from the Arabic al-kīmīā (الكيمياء). The Arabic term is derived from the Greek χημία or χημεία. However, the ultimate origin of the root word, chem, is uncertain.
According to the Oxford English Dictionary, the majority theory is that al-kīmīā is derived from χημία, which is derived from the ancient Egyptian name of Egypt (khem, khame, or khmi, meaning "black earth", contrasting with the surrounding desert.) Therefore, alchemy is the "Egyptian art". However, it is also possible that al-kīmīā derived from χημεία, meaning "cast together".
Traditionally, the science of alchemy was once considered to have sprung from great Egyptian figure named by the Greeks "Hermes Trismegistus" (the "thrice-great" Hermes, celebrated as priest, king, and scholar), who is thought to have been the founder of the art. Reputed to have lived about 1900 BC, he was highly celebrated for his wisdom and skill in the operations of nature. In 1614 Isaac Casaubon demonstrated that the works attributed to Hermes – the so-called "Hermetic corpus" – were actually written pseudonymously during the first three centuries of the Common Era.
List of The New Batman Adventures episodes
Three years after the second season of Batman: The Animated Series ended production, the show was moved (as The New Batman Adventures) from Fox to The WB channel, which was airing and producing Superman: The Animated Series. These shows were merged as part of an hour-long segment called The New Batman/Superman Adventures. The WB wanted more episodes of Batman, so 24 new episodes were produced, which featured a different format and more focus on Batman's supporting cast.
In addition to the network's demands, the producers decided to make the show match the graphic style of Superman: The Animated Series, so all the characters and objects were redesigned as more "animation friendly" with fewer lines, usually referred to by the fans and creative staff as the "revamp" (or alternately, the "new look"). A similar graphic style was used in the rest of the DCAU later on.
The DVD box set of the series is labeled Batman: The Animated Series – Volume Four (from The New Batman Adventures), most likely to establish the connection with the original series.
Chemistry (Smash)
"Chemistry" is the sixth episode of the American television series, Smash. The episode aired on March 12, 2012.
Plot
Ivy (Megan Hilty) comes down with laryngitis, Julia (Debra Messing) keeps bumping into Michael (guest star Will Chase), Eileen (Anjelica Huston) and Ellis (Jamie Cepero) talk at a bar, Karen (Katharine McPhee) performs for a bar mitzvah.
Production
Recurring guest stars include Will Chase as actor Michael Swift.
One of the cover songs already announced is "Shake It Out" by Florence + the Machine performed by Katharine McPhee. Additionally, "History is Made at Night" performed by Megan Hilty, Chase and the cast of Marilyn will make a reappearance in this episode, having first been heard in the episode "The Cost of Art", and Hilty's solo version of "Let Me Be Your Star" first heard in the pilot will be heard in the episode. Also, Hilty's version of Jessie J's "Who You Are" was also in the episode. Only "History is Made at Night" was made available as a single on iTunes.
