Encyclopedia of Chemistry

centrations of the products remain constant. Also
called the law of chemical equilibrium.

chemical flux A concept related to RATE OF REAC-
TION, particularly applicable to the progress in one
direction only of component reaction steps in a complex
system or to the progress in one direction of reactions in
a system at dynamic equilibrium (in which there are no
observable concentration changes with time).
See alsoORDER OF REACTION; RATE-LIMITING STEP;
STEADY STATE.

chemical formula A scientific notation in which the
composition of a compound is illustrated. It consists of
atomic symbols for the various elements of the com-
pound together with numerical subscripts indicating
the ratio in which the atoms combine.

chemical kinetics The study of rates and mecha-
nisms of CHEMICAL REACTIONs.

chemical periodicity Properties of the elements are
periodic functions of atomic number. As you move
from left to right in a row of the periodic table, the

properties of the elements change gradually, but at the

end of each row a drastic shift in chemical properties

occurs. The next element in order of atomic number is

more chemically similar to the first element in the row

above it; thus a new row begins on the table. There-

fore, chemical periodicity is the variations in properties

of elements with their position in the periodic table.

chemical property The characteristics of a substance

that describe how it undergoes or resists change to

form a new substance.

chemical reaction A process that results in the inter-

conversion of CHEMICAL SPECIES. Chemical reactions may

chemical reaction 47

Female scientist in a laboratory writes a chemical formula on glass

while observed by a male scientist. Both scientists are wearing

protective white coats and safety glasses. H 3 O+, written on the

glass, is a water molecule with an extra hydrogen atom. At ordi-

nary temperatures, two molecules of water are in equilibrium with

H 3 O+and OH–.(Courtesy of Tek Image/Science Photo Library)

Metal displacement reaction. Experiment demonstrating the dis-
placement of silver from solution by copper.(Courtesy Jerry
Mason/Photo Researchers, Inc.)