Langmuir’s discoveries helped shape the establish-
ment of modern radio and television broadcasting,
safeguarded the lives of soldiers in war, and provided
the framework that allowed his research team to
develop a key to possibly control the weather. Bernard
Vonnegut’s brother, the writer Kurt Vonnegut, made
Langmuir a character, Dr. Felix Hoenikker, in his novel
Cat’s Cradle.Vonnegut claims that the absentminded
scientist really did leave a tip for his wife after break-
fast one time and abandoned his car in the middle of a
traffic jam.
lanthanide contraction The ionic radii decrease
smoothly across the lanthanide series in the PERIODIC
TABLE. Caused by the increase in effective nuclear
charge across the series due to the poor shielding abil-
ity of 4felectrons.
lanthanides The elements 58 to 71 (after lanthanum)
that are very reactive and electropositive. Sometimes
includes lanthanum (La). They are characterized by
having a partially filled set of forbitals in the n= 4
shell.
laser Acronym for light amplification by stimulated
emission of radiation. A device that has mirrors at the
ends and is filled with material such as crystal, glass,
liquid, gas, or dye that has atoms, ions, or molecules
capable of being excited to a metastable state by light,
electric discharge, or other stimulus. The transition
from the metastable state back to the normal ground
state is accompanied by the emission of photons that
form a straight, coherent beam. Laser light is direc-
tional and covers a narrow range of wavelengths. It is
more coherent than ordinary light.
latentiated drug SeeDRUG LATENTIATION.
latex A polymer of cis-1-4 isoprene; milky sap from
the rubber tree Hevea brasiliensis.
lattice The positioning of atoms in crystalline solids.
lattice energy The amount of energy required to sep-
arate ions or molecules in a mole of a crystalline com-
pound.law of combining volumes(Gay-Lussac’s law) At
constant temperature and pressure, the volumes of
reacting gases are expressed as ratios of small whole
numbers.law of conservation of energy Energy cannot be
created or destroyed, just transformed.law of conservation of matter Matter cannot be
created or destroyed in an isolated system.law of conservation of matter and energy The
total amount of matter and energy available in the uni-
verse is fixed.law of definite proportions(law of constant compo-
sition) Different samples of a pure compound will
always contain the same elements in the same propor-
tions by mass.law of partial pressures(Dalton’s law) Total pres-
sure exerted by a mixture of gases is the sum of the
partial pressures of the individual gases.law of partial pressures 161Lattice. The positioning of atoms in crystalline solids