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39 Cards in this Set
- Front
- Back
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acid-dissociation constant (Ka) |
The equilibrium constant for the reaction of the acid with water to generate H3O+. Ka = [H3O+][A−]/[HA] The negative logarithm of Ka is expressed as pKa:pKa = -logKa |
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Arrhenius definitions for acids and bases |
acid: dissociates in water to give H3O+ base: dissociates in water to give -OH |
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Brønsted–Lowry definitions for acids and bases |
acid: proton donor base: proton acceptor |
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Lewis definitions for acids and bases |
acid: electron-pair acceptor (electrophile) base: electron-pair donor (nucleophile) |
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conjugate acid |
The acid that results from protonation of a base. |
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conjugate base |
The base that results from loss of a proton from an acid. |
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covalent bonding |
Bonding that occurs by the sharing of electrons in the region between two nuclei. single, double, or triple |
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curved-arrow formalism |
A method of drawing curved arrows to keep track of electron movement from nucleophile toelectrophile (or within a molecule) during the course of a reaction. (p. 32) |
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degenerate orbitals |
Orbitals with identical energies. (p. 5) |
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delocalized charge |
A charge which is spread out over two or more atoms. We usually draw resonance forms to showhow the charge can appear on each of the atoms sharing the charge. (p. 14) |
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dipole moment (mu) |
A measure of the polarity of a bond (or a molecule), proportional to the product of the chargeseparation times the bond length. (p. 10) |
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electron density |
The relative probability of finding an electron in a certain region of space. |
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electronegativity |
A measure of an element’s ability to attract electrons. Elements with higher electronegativitiesattract electrons more strongly. (p. 10) |
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electrophile |
An electron-pair acceptor (Lewis acid) |
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electrostatic potential map (EPM) |
A computer-calculated molecular representation that uses colors to show the charge distribution ina molecule. Red to show electron-rich regions (most negative electro-static potential) and blue/purple to show electron-poor regions (most positive electro- static potential). The intermediate colors show regions with intermediate potentials. (p. 10) |
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empirical formula |
The ratios of atoms in a compound. |
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formal charges |
A method for keeping track of charges, showing what charge would be on an atom in a particu-lar Lewis structure. |
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Hund’s rule |
When there are two or more unfilled orbitals of the same energy (degenerate orbitals), the lowest-energy configuration places the electrons in different orbitals (with parallel spins) rather thanpaired in the same orbital. |
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inductive effect |
Electron donation or withdrawal through the sigma bonds of a molecule. |
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ionic bonding |
Bonding that occurs by the attraction of oppositely charged ions. Ionic bonding usually resultsin the formation of a large, three-dimensional crystal lattice. |
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isotopes |
Atoms with the same number of protons but different numbers of neutrons; atoms of the sameelement but with different atomic masses. |
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Lewis structure |
A structural formula that shows all valence electrons, with the bonds symbolized by dashes or by pairs of dots, and nonbonding electrons symbolized by dots. |
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line–angle formula |
(skeletal structure, stick figure) A shorthand structural formula with bonds represented bylines. C atoms are implied wherever two lines meet or a line begins or bends. Atoms otherthan C and H are drawn in, but H atoms are not shown unless they are on an atom that isdrawn. Each C atom is assumed to have enough hydrogens to give it four bonds. (p. 20) |
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lone pair |
A pair of nonbonding electrons. |
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molecular formula |
The number of atoms of each element in one molecule of a compound. |
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node |
A region in an orbital with zero electron density. |
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nodal plane |
A flat (planar) region of space with zero electron density. |
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nonbonding electrons |
Valence electrons that are not used for bonding. A pair of nonbonding electrons is often calleda lone pair. |
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nucleophile |
An electron-pair donor (Lewis base) |
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octet rule |
Atoms generally form bonding arrangements that give them filled shells of electrons (noble-gas con-figurations). For the second-row elements, this configuration has eight valence electrons. |
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orbital |
An allowed energy state for an electron bound to a nucleus; the probability function that definesthe distribution of electron density in space. The Pauli exclusion principle states that up to twoelectrons can occupy each orbital if their spins are paired. |
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organic chemistry |
New definition: The chemistry of carbon compounds. Old definition: The study of compoundsderived from living organisms and their natural products. |
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pH |
A measure of the acidity of a solution, defined as the negative logarithm of the H3O+concentration: pH = -log[H3O+] |
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polar covalent bond |
A covalent bond in which electrons are shared unequally. A bond with equal sharing of electronsis called a nonpolar covalent bond. |
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resonance hybrid |
A molecule/ion for which two/more valid Lewis structures can be drawn, differing only inthe placement of the valence electrons. These are called resonance forms/structures. Individual resonance forms do not exist, but we can estimate their relative energies. The more important (lower-energy) structures are called major contributors, andthe less important (higher-energy) structures are called minor contributors. When a charge isspread over two/more atoms by resonance, it is "delocalized" and the molecule is "resonance stabilized". |
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structural formulas |
A complete structural formula (such as a Lewis structure) shows all the atoms and bonds inthe molecule. A condensed structural formula shows each central atom along with the atomsbonded to it. A line–angle formula assumes that there is a carbon atom wherever two lines meet or a line begins or ends. |
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valence |
The number of bonds an atom usually forms. |
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valence electrons |
Those electrons that are in the outermost shell. |
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vitalism |
The belief that syntheses of organic compounds require the presence of a “vital force.” |
