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
Gauss's principle of least constraint kinetic energy formula_10 is also conserved under these conditions Since the line element formula_12 in the formula_13-dimensional space of the coordinates is defined the conservation of energy may also be written Dividing formula_16 by formula_17 yields another minimal quantity Since formula_19 is the local curvature of the trajectory in the formula_13-dimensional space of the coordinates, minimization of formula_21 is equivalent to finding the trajectory of least curvature (a geodesic) that is consistent with the constraints. Hertz's principle is also a special case of Jacobi's formulation of the least-action principle. Gauss's principle of least constraint The principle of least constraint is