Period 2 element two make up all natural occurrence of lithium on Earth, although further isotopes have been synthesized. In ionic compounds, lithium loses an electron to become positively charged, forming the cation Li. Lithium is the first alkali metal in the periodic table, and the first metal of any kind in the periodic table. At standard temperature and pressure, lithium is a soft, silver-white, highly reactive metal. With a density of 0.564 g·cm, lithium is the lightest metal and the least dense solid element. Lithium is one of the few elements synthesized in the Big Bang, making it a primordial element. Lithium
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