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A Nonpolar Molecule is a system in which the net partial positive charge and net partial negative charge occur at the same location. As a result, the system lacks a net dipole. There may be individual dipoles in the bonds, but because of geometric arrangements, they effectively cancel each other out. Nonpolar systems are usually characterized as having high levels of symmetry overall. Nonpolar systems will have characteristics that are attributed to the lack of charges.  |
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The Octahedron is a geometric pattern that is used for any atom that has expanded its octet to contain a total of six electron pairs. The structure is characterized as being highly symmetrical. It consists of 3 - 1800 bond angles and 12 -900 bond angles.  |
| The Octet Rule is a major component of doing Lewis Dot Structures. The rule states that all covalently bonded atoms will strive to surround themselves with four pairs of electrons, or eight electrons. The four pairs correspond to the number of electron pairs found in the valence levels of the most stable elements, the Noble Gases. The primary exception to the four pairs will occur with some atoms such as Hydrogen which will try to duplicate the structure of Helium by surrounding itself with one pair of electrons. In addition, some atoms in more exotic molecules will periodically violate the Octet Rule and surround themselves with more than four electron pairs. |
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A Polar Molecule is a structure in which the net partial positive charge and the net partial negative charge in the structure will be found at different locations. This will cause the system to have a somewhat negative side and a corresponding positive side. As a result, the system behaves much like a magnet with a North pole and a South pole. Polar molecules will respond to any areas of charge that are near them. The characteristics of polar molecules will be influenced by the presence of these two areas of charge.  |
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Pyramidal Geometry is a shape that is associated with molecular geometry. It occurs in molecules that contain four atoms. One of the atoms is located in a central position and the other three atoms are bonded to it. The three external atoms are usually in a single plane, but will not be in the same plane with the central atom. The pyramidal shape is most commonly associated with systems that have a tetrahedral geometry for the central atom. The bond angles in these structures will be close to 109.50.  |
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Resonance is a process available to covalently bonded molecules that will allow them to increase their stability. The process involves the continuous movement of a multiple bond, usually a double bond, from one position to another. This results in a series of structures that are identical in all ways except for the location of the multiple bond. In order for resonance to occur, the changing multiple bonds must always be located between the exact same type of atoms. The more different resonance structures that a molecule uses, the more the resulting increase in stability of the system.  |
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Tetrahedral Geometry occurs around any atom that has a combined total of four bonded atoms or nonbonded electron pairs attached to it. The four groups arrange themselves in this geometric pattern to achieve maximum stability by maintaining minimum repulsion between the electron pairs. The angles in this shape consist of a total of six angles at 109.50.  |
Trigonal Bipyramid
The Trigonal Bipyramid is a geometric pattern that is used by any atom which has expanded its octet to maintain a combined total of five bonded atoms or nonbonded electron pairs. The shape consists of three equatorial positions and two axial positions. Within the structure there are three different size bond angles. The shape contains three angles of 1200, two angles of 1800 and six angles of 900.
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Trigonal Planar geometry is a shape that is used by an atom that is attached to a combined total of three bonded atoms and nonbonded electron pairs. This shape is usually associated with a system that has two single bonds and one double bond. The structure contains three angles of 1200. All four positions in this geometric shape are located on the same plane. If the three external positions are moved into a different plane from the central atom, then the structure changes into a pyramid.  |
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Valence Shell Electron Pair Repulsion Theory is a concept that is used to interpret the geometric patterns employed by atoms and molecules in systems that are covalently bonded. The Theory is based on the idea that all the electron pairs that are directly attached to an atom, whether as bonded pairs or nonbonded pairs, will arrange themselves to be as far away from each other as possible. They will adopt a shape so that the repulsions between these pairs will be evenly distributed and at a minimum. As a result of these repulsions, the individual atoms will achieve specific types of geometry.
In this context, a group is a bonded atom or a nonbonded electron pair. Single bonds, double bonds and triple bonds are basically treated as if they are all the same. |
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