Lanthanide Series

Elements that have incompletely filled 4f subshells or readily give rise to cations that have incompletely filled 4f subshells.

Lattice Energy

The energy required to completely separate one mole of a solid ionic compound into gaseous ions.

Lattice Points

The positions occupied by atoms, molecules, or ions that define the geometry of a unit cell.

Law

A concise verbal or mathematical statement of a relationship between phenomena that is always the same under the same conditions.

Law of Conservation of Energy

The total quantity of energy in the universe is constant.

Law of Conservation of Mass

Matter can be neither created nor destroyed.

Law of Definite Proportions

Different samples of the same compound always contain its constituent elements in the same proportions by mass.

Law of Mass Action

For a reversible reaction at equilibrium and a constant temperature, a certain ratio of reactant and product concentrations has a constant value, K (the equilibrium constant).

Law of Multiple Proportions

If two elements can combine to form more than one type of compound, the masses of one element that combine with a fixed mass of the other element are in ratios of small whole numbers.

Le Chatelier’s Principle

If an external stress is applied to a system at equilibrium, the system will adjust itself in such a way as to partially offset the stress as the system reaches a new equilibrium position.

Lewis Acid

A substance that can accept a pair of electrons.

Lewis Base

A substance that can donate a pair of electrons.

Lewis Dot Symbol

The symbol of an element with one or more dots that represent the number of valence electrons in an atom of the element.

Lewis Structure

A representation of covalent bonding using Lewis symbols. Shared electron pairs are shown either as lines or as pairs of dots between two atoms, and lone pairs are shown as pairs of dots on individual atoms.

Ligand

A molecule or an ion that is bonded to the metal ion in a complex ion.

Limiting Reagent

The reactant used up first in a reaction.

Line Spectra

Spectra produced when radiation is absorbed or emitted by substances only at some wavelengths.

Lipids

A group of biological fats that contain the ester functional group.

Liquid

One of the three states of matter. A liquid fills a container to the extent of its own volume and thus forms a surface.

Liter

The volume occupied by one cubic decimeter.

Lone Pairs

Valence electrons that are not involved in covalent bond formation.