percent yield The percent yield (% yield) is the
actual yield divided by the theoretical yield, with
the resultant multiplied by 100.
periodsPeriods are the horizontal rows on the peri-
odic table that have consecutive atomic numbers.
phase changes Phase changes are changes of state.
phase diagram A phase diagram is a graph repre-
senting the relationship of the states of matter of
a substance to temperature and pressure.
pi (π) bonds Pi bonds result from the overlap of
atomic orbitals on both sides of a line connecting
two atomic nuclei.
polar covalent bonds Polar covalent bonds are
covalent bonds in which there is an unequal
sharing of the bonding pair of electrons.
polyprotic acids Polyprotic acids are acids that can
donate more than one proton.
potential energy Potential energy is stored energy.
positron A positron is essentially an electron that
has a positive charge instead of a negative one.
precipitate A precipitate is an insoluble product
that forms in a solution; the formation of a solid
from ions in solution.
precipitation reactions Precipitation reactions are
reactions that involve the formation of an insoluble
compound, a precipitate, from the mixing of two
soluble compounds.
pressure Pressure is the force exerted per unit of
surface area.
principal quantum number (n) The principal quan-
tum number describes the size of the orbital and
relative distance from the nucleus.
proof The proof of an aqueous ethyl alcohol solu-
tion is twice the volume percent.
quantized Quantized means that there could be
only certain distinct energies associated with a
state of the atom.
quantum numbers Quantum numbers are used to
describe each electron within an atom correspon-
ding to the orbital size, shape, and orientation in
space.
radioactivity Radioactivity is the spontaneous decay
of an unstable isotope to a more stable one.
rate constant (k) The rate constant is a proportion-
ality constant that appears in the rate law and
relates the concentration of reactants to the speed
of reaction.
rate-determining step The rate-determining step is
the slowest one of the reaction steps and controls
the rate of the overall reaction.
rate equation The rate equation relates the speed of
reaction to the concentration of reactants and has
the form: Rate =k[A]m[B]n.... where k is the rate
constant and mand nare the orders of reaction
with respect to that specific reactant.
reactants The starting materials in a chemical
reaction, which get converted into different
substances called products.
reaction intermediateA reaction intermediate is
a substance that is formed but then consumed
during the reaction mechanism.
reaction mechanism The reaction mechanism is
the sequence of individual reactions that occur in
an overall reaction in going from reactants to
products.
reaction quotient The reaction quotient, Q, is the
numerical value that results when non-equilibrium
concentrations are inserted into the equilibrium
expression. When the system reaches equilibrium,
the reaction quotient becomes the equilibrium
constant.
reactive siteThe reactive site of a molecule is the
place at which the reaction takes place.
redox reactions Redox reactions are chemical
reactions in which electrons are lost and gained.
reducing agentThe reactant undergoing oxidation
in a redox reaction is called the reducing agent.
reductionReduction is the gain of electrons in
a redox reaction.
resonance Resonance is a way of describing a
molecular structure that cannot be represented by
a single Lewis structure. Several different Lewis
structures are used, each differing only by the
position of electron pairs.
reverse osmosis Reverse osmosis takes place when
the pressure on the solution side exceeds the
osmotic pressure and solvent molecules are forced
back through the semipermeable membrane into
the solvent side.
root mean square speedThe average velocity of
the gas particles is called the root mean square
speed.
salt bridge A salt bridge is often an inverted U-tube
that contains a gel containing a concentrated
electrolyte solution, used in an electrochemical
cell to maintain electrical neutrality in the cell
compartments.
saturated hydrocarbonsSaturated hydrocarbons
are hydrocarbons that are single bonded to the
maximum number of other atoms.364 Glossary