Term
| Lewis structure; Lewis formula |
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Definition
| a structural formula consisting of electron-dot symbols, with lines as bonding pairs and dots as lone pairs |
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Term
| resonance structure; resonance form |
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Definition
| one of two or more Lewis structures for a molecule that cannot be adequately depicted by a single structure. Resonance structures differ only in the position of bonding and lone electron pairs. |
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Definition
| The weighted average of the resonance structures of a molecule. |
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Term
| (electron-pair) delocalization |
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Definition
| The process by which electron density is spread over several atoms rather than remaining between two. |
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Definition
| The hypothetical charge on an atom in a molecule or ion, equal to the number of valence electrons minus the sum of all the unshared and half the shared valence electrons. |
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Definition
| Referring to a bonded atom, such as Be or B, that has fewer than eight valence electrons. |
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Definition
| A molecular or atomic species with one or more unpaired electrons, which typically make it very reactive. |
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Definition
| A valence level that can accommodate more than 8 electrons by using available d orbitals; occurs only for elements in Period 3 or higher. |
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| valence-shell electron-pair repulsion (VSEPR) theory |
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Definition
| a model explaining that the shapes of molecules and ions result from minimizing electron-pair repulsions around a central atom. |
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Definition
| The three-dimensional structure defined by the relative positions of the atomic nuclei in a molecule. |
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Definition
| The angle formed by the nuclei of two surrounding atoms with the nucleus of the central atom at the vertex. |
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Definition
| The geometric arrangement obtained when two electron groups minimize their separation around a central atom. |
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Definition
| A molecular shape formed by three atoms lying in a straight line, with a bond angle of 180 degrees (shape class AX_2 or AX_2_E_3). |
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Term
| trigonal planar arrangement |
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Definition
| The geometric arrangement formed when three electron groups maximize their separation around a central atom. |
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Term
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Definition
| A molecular shape that arises when a central atom is bonded to two other atoms and has one or two lone pairs; occurs as the AX_2E shape class (bond angle < 120 degrees) in the trigonal planar arrangement and as the AX_2E_2 shape class (bond angle < 109.5 degrees) in the tetrahedral arrangement. |
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Definition
| The geometric arrangement formed when four electron groups maximize their separation around a central atom; when all four groups are bonding groups, the molecular shape is tetrahedral (AX_4; ideal bond angle 109.5 degrees) |
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Definition
| A molecular shape (AX_3) caused by the presence of one lone pair in a tetrahedral arrangement. |
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Term
| trigonal bipyramidal arrangement |
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Definition
| The geometric arrangement formed when five electron groups maximize their separation around a central atom. When all five groups are bonding groups, the molecular shape is trigonal bipyramidal (AX_5; ideal bond angles, axial-center-equatorial 90 degrees and equatorial-center-equatorial 120 degrees) |
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Definition
| An atom (or group) that lies in the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule. |
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Definition
| An atom (or group) that lies above or below the trigonal plane of a trigonal bipyramidal molecule, or a similar structural feature in a molecule. |
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Definition
| A molecular shape caused by the presence of one equatorial lone pair in a trigonal bipyramidal arrangement (AX_4E) |
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Definition
| A molecular shape caused by the presence of two equatorial lone pairs in a trigonal bipyramidal arrangement (AX_3E_2) |
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Definition
| The geometric arrangement obtained when six electron groups maximize their space around a central atom; when all six groups are bonding groups, the molecular shape is octahedral (AX_6; ideal bond angle = 90 degrees) |
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Definition
| A molecular shape (AX_4E_2) caused by the presence of two axial lone pairs in an octahedral arrangement. |
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Definition
| The overall distribution of electronic charge in a molecule, determined by its shape and bond polarities. |
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