Glossary of chemical terms

laminar flow
	Laminar flow is smooth, uniform, non-turbulent flow of a gas or liquid in parallel layers, with little mixing between layers. It is characterized by small values of the Reynolds number.
lanthanides
	Lanthanides (lanthanons, lanthanoids or rare-earth elements) are a series of fourteen elements in the periodic table, generally considered to range in proton number from cerium to lutetium inclusive. It was convenient to divide these elements into the cerium group or light earth: cerium (Ce), praseodymium (Pr), neodymium (Nd), promethium (Pm), samarium (Sm), europium (Eu); and the yttrium group or heavy earths: gadolinium (Gd), terbium (Tb), dysprosium (Dy), holmium (Ho), erbium (Er), thulium (Tm), ytterbium (Yb) i lutetium (Lu). The position of lanthanum is somewhat equivocal and, although not itself a lanthanides, it is often included with them for comparative purpose. The lanthanides are sometimes simply called the rare earths. Apart from unstable Pm the lanthanides are actually not rare. Cerium is the 26. most abundant of all elements, 5 times as abundant as Pb. All are silvery very reactive metals.
laser
	Laser (light amplification by stimulated emission of radiation) is a light amplifier usually used to produce monochromatic coherent radiation in the infrared, visible, and ultraviolet regions of the electromagnetic spectrum.
latent heat
	Latent Heat (L) is the quantity of heat absorbed or released when a substance changes its physical phase at constant temperature (e.g. from solid to liquid at the melting point or from liquid to gas at the boiling point).
lattice constants
	Lattice constants are parameters specifying the dimensions of a unit cell in a crystal lattice, specifically the lengths of the cell edges and the angles between them.
lattice energy
	Lattice energy is the energy per ion pair required to separate completely the ions in a crystal lattice at a temperature of absolute zero.
Le Chatelier's principle
	The idea that a system at equilibrium will respond to a stress placed upon it in such a manner as to partially offset that stress. The principle was first stated in 1888 by French physical chemist Henri Le Chatelier (1850-1936).
Lewis acid
	Lewis acid is an agent capable of accepoting a pair of electrons to form a coordinate bond.
Lewis base
	Lewis base is an agent capable of donating a pair of electrons to form a coordinate bond.
ligand
	Ligand is an ion (F-, Cl-, Br-, I-, S2-, CN-, NCS-, OH-, NH2-) or molecule (NH3, H2O, NO, CO) that donates a pair of electron to a metal atom or ion in forming a coordination complex.
ligand field theory
	Ligand field theory is a description of the structure of crystals containing a transition metal ion surrounded by nonmetallic ions (ligands). It is based on construction of molecular orbitals involving the d-orbitals of the central metal ion and combinations of atomic orbitals of the ligands.
light year
	Light year (ly) is a unit of distance used in astronomy, defined as the distance light travels in one year in a vacuum (ly = 9.46052973∙1015).
lignins
	Lignins are macromolecular constituents of wood related to lignans, composed of phenolic propylbenzene skeletal units, linked at various sites and apparently randomly.
lipids
	Lipids are a loosely defined term for substances of biological origin that are soluble in nonpolar solvents. They consist of saponifiable lipids, such as glycerides (fats and oils) and phospholipids, as well as nonsaponifiable lipids, principally steroids.
liter
	Liter (l, L) is a synonym for cubic decimeter (L = dm3).
lithosphere
	Lithosphere is the outer layer of the solid earth, extending from the base of the mantle to the surface of the crust.
LPG
	LPG (Liquid Petroleum Gas) is a mixture of short hydrocarbons with most of the volume being propane and butane. LPG is considered an alternative fuel that burns cleaner than gasoline.
lumen
	Lumen (lm) is the SI derived unit of luminous flux. The lumen is the luminous flux emitted in a solid angle of one steradian by a point source having a uniform intensity of one candela (1lm =1 cd∙sr).
luminous flux
	Luminous flux (Φ) is the intensity of light from a source multiplied by the solid angle. The SI unit is lumen.
lux
	Lux (lx) is the SI derived unit of illuminance. The lux is the illuminance produced by a luminous flux of one lumen uniformly distributed over a surface of one square metre (lx = lm·m-2).
Lyman series
	Lyman series is the series of lines in the spectrum of the hydrogen atom which corresponds to transitions between the ground state (principal quantum number n = 1) and successive excited states.

 

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