Lithium Lithium Lithium (from ) is a chemical element with symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the lightest metal and the lightest solid element. Like all alkali metals, lithium is highly reactive and flammable, and is stored in mineral oil. When cut, it exhibits a metallic luster, but moist air corrodes it quickly to a dull silvery gray, then black tarnish. It never occurs freely in nature, but only in (usually ionic) compounds, such as pegmatitic minerals which were once the main source of lithium. Due to its solubility
Eckart conditions better understanding of the Eckart frame it may be useful to remark that it becomes a principal axes frame in the case that the molecule is a rigid rotor, that is, when all "N" displacement vectors are zero. The "N" position vectors formula_11 of the nuclei constitute a 3"N" dimensional linear space R: the "configuration space". The Eckart conditions give an orthogonal direct sum decomposition of this space The elements of the 3"N"-6 dimensional subspace R are referred to as "internal coordinates", because they are invariant under overall translation and rotation of the molecule and, thus, depend only on the