| Effective nuclear charge |
the portion of the nuclear charge that is experienced by the
highest energy level electrons |
| Effusion |
the flow of a gas through a hole of dimensions small in
comparison with the distance between molecules |
| Elastomer |
a material that recovers its shape after a deforming force is
removed |
| Electrical conductivity |
the ability to conduct an electric current |
| Electrochemistry |
the study of the interchange of chemical and electrical
energy |
| Electrode potential |
the driving force of a voltaic half-cell |
| Electrolysis |
the passage of an electric current through a substance in
order to cause a chemical change; the use of electric energy to produce an
oxidation-reduction process |
| Electrolyte |
a substance that dissolves or melts to form ions so that the
resulting liquid is capable of conducting an electrical current |
| Electrolytic cell |
a cell in which external electric energy causes an
oxidation-reduction reaction to occur |
| Electromagnetic energy |
radiant energy; waves propagated by periodic variations of
electric and magnetic field energy |
| Electromagnetic radiation |
radiant energy that exhibits wavelike behavior and travels
through space at the speed of light |
| Electron |
a negatively charged particle that moves around the nucleus
of an atom |
| Electron affinity |
the energy change associated with the addition of an electron
to a gaseous atom |
| Electron capture |
a process in which one of the inner-orbital electrons in an
atom is captured by the nucleus |
| Electron sea model |
a model for metals postulating a regular array of cation sin
a "sea" of electrons |
| Electron spin quantum number |
a quantum number representing one of the two possible values
for the electron spin; either -1/2 or 1/2. |
| Electronic spectra |
absorption spectra resulting from the excitation of molecules
between electronic energy states; ultraviolet and visible spectra |
| Electronegativity |
the relative ability of an atom to attract electrons to
itself from a chemical bond |
| Electrophoresis |
the migration of colloidal particles in an electric field by
virtue of their charge |
| Element |
a substance that cannot be decomposed into simpler substances
by chemical or physical means |
| Elementary process |
the individual steps of a reaction mechanism |
| Elementary step |
a reaction whose rate law can be written from its
molecularity |
| Empirical formula |
the simplest whole number ratio of atoms in a compound |
| Emulsifying agent |
a substance having both hydrophilic and hydrophobic character
that acts to stabilize an emulsion |
| Enantiomers |
nonsuperimposable mirror images |
| Endothermic |
refers to a reaction where energy (as heat) flows into the
system |
| End point |
the point in a titration at which the indicator changes color |
| Energy |
the capacity to do work or to cause heat flow |
| Enthalpy |
a property of a system equal to E + PV,
where E is the internal energy of the system, P is the pressure, and V
is the volume of the system. At constant pressure, the change in enthalpy equals the
energy flow as heat |
| Enthalpy of fusion |
the energy necessary to change a solid to a liquid at the
melting point |
| Enthalpy of solution |
the enthalpy change accompanying the dissolution of a solute
in a solvent |
| Enthalpy of solvation |
the enthalpy change attending the association of solute
particles with solvent molecules |
| Enthalpy of vaporization |
the energy required to convert a liquid to its vapor at the
boiling point |
| Entropy |
a measure of the degree of disorder or randomness in a system |
| Enzyme |
large, protein-containing molecules that catalyze biochemical
reactions |
| Equatorial bonds |
bonds radiating out from the center of a molecule around its
equator |
| Equilibrium |
the state of a system in which opposing forces or rates are
in balance so that no net change occurs |
| Equilibrium constant |
a quantitative index of the relative amounts of products and
reactants present at equilibrium |
| Equilibrium expression |
the expression obtained by multiplying the product
concentrations and dividing by the multiplied reactant concentrations, and dividing by the
multiplied reactant concentrations, with each concentration raise to a power represented
by the coefficient in the balanced reaction |
| Equilibrium position |
a particular set of equilibrium concentrations |
| Equivalence point |
the point in a titration when enough titrant has been added
to react exactly with the substance in solution being titrated |
| Essential elements |
the elements known to be essential to human life |
| Ester |
an organic compound produced by the reaction between a
carboxylic acid and an alcohol |
| Ether |
a compound containing an oxygen atom attached to two
hydrocarbon residues |
| Excited state |
any energy state higher than the ground state |
| Exclusion principle |
no two electrons in an atom can have the same four quantum
numbers |
| Exothermic |
refers to a reaction where energy (as heat) flows out of the
system |
| Extensive property |
a property, such as mass or volume, that depends on the
quantity of material in an object |
| Extrinsic semiconductor |
a semiconductor in which electric conduction is dependent
upon the presence of an impurity |
