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
Dense set space "X" is the least cardinality of a dense subset of "X". An alternative definition of dense set in the case of metric spaces is the following. When the topology of "X" is given by a metric, the closure formula_1 of "A" in "X" is the union of "A" and the set of all limits of sequences of elements in "A" (its "limit points"), Then "A" is dense in "X" if Note that formula_4. If formula_5 is a sequence of dense open sets in a complete metric space, "X", then formula_6 is also dense in "X". This fact is one