Chemistry Glossary: (A)
Absolute zero the lowest possible temperature, -273.15oC (0 Kelvin); at this temperature, molecules are at their lowest energy state
Absorbance the extent to which radiant energy is absorbed by a substance
Absorption spectra spectra resulting from the adsorption of radiant energy by molecules and ions
Accuracy the correctness of the value obtained in a measurement
Acidic anhydride a nonmetal oxide that can combine with water to form an acid
Acid a substance that produces hydrogen ions in solution; a proton donor
Acid-base indicators a substance that marks the endpoint of an acid-base titration by changing color
Acid dissociation constant (Ka) the equilibrium constant for a reaction in which a proton is removed from an acid by H2O to form the conjugate base and H3O+
Acidic oxide a covalent oxide that dissolves in water to give an acidic solution
Actinides the 14 inner transition metals beginning with actinium
Activated complex (transition states) the arrangement of atons found at the top of potential energy barrier as a reaction proceeds from reactants to products
Activation energy the threshold energy that much be overcome to produce a chemical reaction
Active site a location on the surface of a heterogeneous catalyst to which reactants bind and at which they pass through the transition state
Addition Polymerization a tye of polymerization in which the monomers simply add together to form the polymer, with no other products
Addition reaction a reaction in which one molecule adds to another without the loss  of atoms from either
Adsorbent a substance having a large surface area to which other surfaces adhere
Adsorption the collection of one substance on the surface of another
Alcohol A compounding containing the hydroxy (O-H) group attached to a hydrocarbon
Aldehyde an organic compound containing the carbonyl group bonded to at least one hydrogen atom
Aliphatic hydrocarbon hydrocarbons of the alkane, alkene, or alkyne groups
Alkali metal a Group 1A metal
Alkaline earth metal a Group 2A metal
Alkane hydrocarbons containing only sigma bonds (single bonds); has a general formula for CnH2n+2
Alkene hydrocarbons containing a pi bond (double); general formula is CnH2n
Alkyne hydrocarbons containing two bonds between adjacent carbon atoms (a triple bond); general formula of CnH2n-2
Allotropism the existence of a substance in more than one form, usually the same state
Alloy a substance that contains a mixture of elements and has metallic properties
Alpha particle (a) a radioactive emission identical with the helium nucleus; He2+
Amalgam An alloy of mercury with one or more other metals
Amide A compound containg the -CON- (C double bonded to O) attached to hydrogen or hydrocarbon residues
Amine an organic base derived from ammonia in which one or more of the hydrogen atons are replaced by organic groups
a-Amino acid an organic acid in which an aminoi group and an R gruop are attached to the carbon atom next to the carboxyl group
Amorphous solid a supercooled liquid with teh external appearance of a solid but not having a crystalline structure
Ampere the unit of measurement of electric current, equal to one coulomb per second
Amphoteric having the ability to react either as an acid or a base
Anion a negatively charged ion, which is accordingly attracted to the anode
Anode the electrode in a galvanic cell at which oxidation occurs
Antibonding molecular orbital an orbital higher in energy than the atomic orbitals of which it is composed
Antineutrino a very small neutral particle emitted along with an electron
Aqueous solution a solution in which water is the dissolving medium or solvent
Aromatic hydrocarbon one of a s special class of cyclic unsaturated hydrocarbons, the simplest of which is benzene
Arrhenius acid a substance that dissociates in aqueous solution to produce hydrogen ions
Arrhenius base a substance that dissociates in aqueous solution to produce hydroxide ions
Arrhenius equation the equation expressing the relationship between the kinetic rate constant and temperature
Atactic chain a polymer chain in which the substituent groups such as CH3 are randomly distributed along the chain
Atmosphere a pressure unit corresponding tothe pressure exerted by the earth's atmosphere at sea level at 0oC, equal to the pressure of a column of mercury 76.0 in height
Atom the smallest part of an element
Atomic mass the average mass of the atoms of an element relative to an atom selected as the standard
Atomic mass unit the unit of atomic masses equal to 1/12 the mass of the carbon isotope having a mass of 12 such units
Atomic number the charge on the nucleus of an atom
Atomic radius half the idistance between the nuclei in a molecule consisting of identical atoms
Atomic solid a solid that contains atoms at the lattice points
Atomic weight the weighted average mass of atoms in a naturally occuring element
Aufbau principle the principle stating that as protons are added one by one to the nucleus to build up the elements electrons are similarly added to hydrogenlike orbitals
Autoionization the transfer of a proton from one molecule to another of the same substance
Average bond energy the average energy per mole required to dissociate bonds of a particular order between two atoms
Avogadro's law equal volumes of gases at teh same temperature and pressure contain the same number of particles
Avogadro's number the number of atoms in exactly 12 grams of puer C-12, equal to 6.022 x 1023
Axial bonds bonds parallel to the axis that is perpendicular to the plane containing the equator of a molecule
Azeotrope a solution of liquids that has a constant boiling point because the composition of the vapor is the same as the composition of the liquid
Azimuthal quantum number (l) the quantum number relating to the shape of an atomic orbital, which can assume any integral value from 0 to  n-1 for each value of n
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