hypervalent molecule

(noun)

A molecule that contains an atom from a main group element which deviates from the octet rule by sharing more than eight electrons.

Related Terms

Examples of hypervalent molecule in the following topics:

  • The Expanded Octet

    • A hypervalent molecule is a molecule that contains one or more main group elements that bear more than eight electrons in their valence levels as a result of bonding.
    • Phosphorus pentachloride (PCl5), sulfur hexafluoride (SF6), chlorine trifluoride (ClF3), and the triiodide ion (I3−) are examples of hypervalent molecules.
    • In the SF6 molecule, the central sulfur atom is bonded to six fluorine atoms, so sulfur has 12 bonding electrons around it.
    • The overall geometry of the molecule is depicted (tetragonal bipyramidal, or octahedral), and bond angles and lengths are highlighted.
    • The overall geometry of the molecule is depicted (trigonal bipyramidal), and bond angles and lengths are highlighted.

  • Bonding in Coordination Compounds: Valence Bond Theory

    • Valence bond theory is used to explain covalent bond formation in many molecules.
    • In 1927, physicist Walter Heitler and collaborator Fritz London developed the Heitler-London theory, which enabled the calculation of bonding properties of the covalently bonded diatomic hydrogen molecule (H2) based on quantum mechanical considerations.
    • Valence bond theory is used to explain covalent bond formation in many molecules, as it operates under the condition of maximum overlap, which leads to the formation of the strongest possible bonds.

  • The Nonclassical Carbocation Hypothesis

    • One of the best criteria for evaluating candidate ions is to establish whether one or more of the participating carbon atoms is hypervalent (has more than four coordinating groups).
    • In the first diagram below, the simplest hypervalent carbocation, methanonium, is drawn on the left in the gray shaded box.

  • 1,2-Group Shifts

    • When alkoxide base is added to silyl ketones, hypervalent silicon intermediates may be formed prior to rearrangement, shown in the fourth diagram above.

  • Homonuclear Diatomic Molecules

    • Diatomic molecules are composed of only two atoms, of either the same or different chemical elements.
    • Common diatomic molecules include hydrogen (H2), nitrogen (N2), oxygen (O2), and carbon monoxide (CO).
    • All diatomic molecules are linear, which is the simplest spatial arrangement of atoms.
    • Translational energies (the molecule moving from point A to point B)
    • A space-filling model of the homonuclear diatomic molecule nitrogen.

  • Molecules

    • Most often, the term "molecules" refers to multiple atoms; a molecule may be composed of a single chemical element, as with oxygen (O2), or of multiple elements, such as water (H2O).
    • Most molecules are too small to be seen with the naked eye.
    • The full elemental composition of a molecule can be precisely represented by its molecular formula, which indicates the exact number of atoms that are in the molecule.
    • Isomers are molecules with the same atoms in different geometric arrangements.
    • Each molecule is a structural isomer of the other.

  • Polyatomic Molecules

    • A polyatomic molecule is a single entity composed of at least three covalently-bonded atoms.
    • Molecules are distinguished from ions by their lack of electrical charge.
    • The science of molecules is called molecular chemistry or molecular physics, depending on the focus.
    • A pure substance is composed of molecules with the same average geometrical structure.
    • Molecules with the same atoms in different arrangements are called isomers.

  • Metabolic Pathways

    • An anabolic pathway requires energy and builds molecules while a catabolic pathway produces energy and breaks down molecules.
    • Another metabolic pathway might build glucose into large carbohydrate molecules for storage.
    • Catabolic pathways involve the degradation of complex molecules into simpler ones, releasing the chemical energy stored in the bonds of those molecules.
    • Anabolic pathways are those that require energy to synthesize larger molecules.
    • Catabolic pathways are those that generate energy by breaking down larger molecules.

  • Outcomes of Glycolysis

    • One glucose molecule produces four ATP, two NADH, and two pyruvate molecules during glycolysis.
    • Glycolysis starts with one molecule of glucose and ends with two pyruvate (pyruvic acid) molecules, a total of four ATP molecules, and two molecules of NADH .
    • Two ATP molecules were used in the first half of the pathway to prepare the six-carbon ring for cleavage, so the cell has a net gain of two ATP molecules and 2 NADH molecules for its use.
    • If the cell cannot catabolize the pyruvate molecules further (via the citric acid cycle or Krebs cycle), it will harvest only two ATP molecules from one molecule of glucose.
    • In this situation, the entire glycolysis pathway will continue to proceed, but only two ATP molecules will be made in the second half (instead of the usual four ATP molecules).

  • Water’s Solvent Properties

    • Water's polarity makes it an excellent solvent for other polar molecules and ions.
    • A polar molecule with partially-positive and negative charges, it readily dissolves ions and polar molecules.
    • The charges associated with these molecules form hydrogen bonds with water, surrounding the particle with water molecules.
    • Water is a poor solvent, however, for hydrophobic molecules such as lipids.
    • Nonpolar molecules experience hydrophobic interactions in water: the water changes its hydrogen bonding patterns around the hydrophobic molecules to produce a cage-like structure called a clathrate.