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Chemistry LibreTexts

4.8: Key Terms

  • Page ID
    478694
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    Example and Directions
    Words (or words that have the same definition)The definition is case sensitive(Optional) Image to display with the definition [Not displayed in Glossary, only in pop-up on pages](Optional) Caption for Image(Optional) External or Internal Link(Optional) Source for Definition
    (Eg. "Genetic, Hereditary, DNA ...")(Eg. "Relating to genes or heredity")The infamous double helix https://bio.libretexts.org/CC-BY-SA; Delmar Larsen
    Glossary Entries
    Word(s)DefinitionImageCaptionLinkSource
    axial positionlocation in a trigonal bipyramidal geometry in which there is another atom at a 180° angle and the equatorial positions are at a 90° angle    
    bond angleangle between any two covalent bonds that share a common atom    
    bond dipole momentseparation of charge in a bond that depends on the difference in electronegativity and the bond distance represented by partial charges or a vector    
    bond distance(also, bond length) distance between the nuclei of two bonded atoms    
    bond energy(also, bond dissociation energy) energy required to break a covalent bond in a gaseous substance    
    bond lengthdistance between the nuclei of two bonded atoms at which the lowest potential energy is achieved    
    Born-Haber cyclethermochemical cycle relating the various energetic steps involved in the formation of an ionic solid from the relevant elements    
    covalent bondbond formed when electrons are shared between atoms    
    dipole momentproperty of a molecule that describes the separation of charge determined by the sum of the individual bond moments based on the molecular structure    
    double bondcovalent bond in which two pairs of electrons are shared between two atoms    
    electron-pair geometryarrangement around a central atom of all regions of electron density (bonds, lone pairs, or unpaired electrons)    
    electronegativitytendency of an atom to attract electrons in a bond to itself    
    equatorial positionone of the three positions in a trigonal bipyramidal geometry with 120° angles between them; the axial positions are located at a 90° angle    
    formal chargecharge that would result on an atom by taking the number of valence electrons on the neutral atom and subtracting the nonbonding electrons and the number of bonds (one-half of the bonding electrons)    
    free radicalmolecule that contains an odd number of electrons    
    hypervalent moleculemolecule containing at least one main group element that has more than eight electrons in its valence shell    
    inert pair effecttendency of heavy atoms to form ions in which their valence s electrons are not lost    
    ionic bondstrong electrostatic force of attraction between cations and anions in an ionic compound    
    lattice energy (ΔHlattice)energy required to separate one mole of an ionic solid into its component gaseous ions    
    Lewis structurediagram showing lone pairs and bonding pairs of electrons in a molecule or an ion    
    Lewis symbolsymbol for an element or monatomic ion that uses a dot to represent each valence electron in the element or ion    
    linearshape in which two outside groups are placed on opposite sides of a central atom    
    lone pairtwo (a pair of) valence electrons that are not used to form a covalent bond    
    molecular structurearrangement of atoms in a molecule or ion    
    molecular structurestructure that includes only the placement of the atoms in the molecule    
    octahedralshape in which six outside groups are placed around a central atom such that a three-dimensional shape is generated with four groups forming a square and the other two forming the apex of two pyramids, one above and one below the square plane    
    octet ruleguideline that states main group atoms will form structures in which eight valence electrons interact with each nucleus, counting bonding electrons as interacting with both atoms connected by the bond    
    polar covalent bondcovalent bond between atoms of different electronegativities; a covalent bond with a positive end and a negative end    
    polar molecule(also, dipole) molecule with an overall dipole moment    
    pure covalent bond(also, nonpolar covalent bond) covalent bond between atoms of identical electronegativities    
    resonancesituation in which one Lewis structure is insufficient to describe the bonding in a molecule and the average of multiple structures is observed    
    resonance formstwo or more Lewis structures that have the same arrangement of atoms but different arrangements of electrons    
    resonance hybridaverage of the resonance forms shown by the individual Lewis structures    
    single bondbond in which a single pair of electrons is shared between two atoms    
    tetrahedralshape in which four outside groups are placed around a central atom such that a three-dimensional shape is generated with four corners and 109.5° angles between each pair and the central atom    
    trigonal bipyramidalshape in which five outside groups are placed around a central atom such that three form a flat triangle with 120° angles between each pair and the central atom, and the other two form the apex of two pyramids, one above and one below the triangular plane    
    trigonal planarshape in which three outside groups are placed in a flat triangle around a central atom with 120° angles between each pair and the central atom    
    triple bondbond in which three pairs of electrons are shared between two atoms    
    valence shell electron-pair repulsion theory (VSEPR)theory used to predict the bond angles in a molecule based on positioning regions of high electron density as far apart as possible to minimize electrostatic repulsion    
    vectorquantity having magnitude and direction    

    4.8: Key Terms is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by LibreTexts.

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