Alkalimetall

Alkalimetall, in English commonly called an alkali metal, refers to the elements in Group 1 of the periodic table: lithium, sodium, potassium, rubidium, cesium, and francium. These metals share several characteristic features: they are soft, silvery metals with a single electron in their outer shell, low densities, and they readily tarnish in air due to oxidation. They are solid at room temperature, and their melting points and ionization energies are relatively low compared with most other elements. Reactivity generally increases down the group.

Chemically, alkali metals form +1 ions and participate in compounds that are typically highly soluble in water. They react vigorously with water to produce hydrogen gas and metal hydroxides, releasing heat: 2 M + 2 H2O → 2 MOH + H2. The heavier members (rubidium, cesium, and especially francium) react more violently with water and air. Because of their high reactivity, these metals are usually stored under oil or in an inert atmosphere to prevent contact with moisture and oxygen.

Occurrence and production are linked to their scarcity in free form. They do not occur as elements in nature and are found in minerals and saline deposits. Industrial production is achieved mainly by electrolysis of molten salts or by reduction of suitable precursors. Common sources include brines and mineral deposits for sodium and potassium, and mineralogical deposits for lithium.

Uses and significance vary by element. Lithium is central to modern rechargeable batteries and ceramics; sodium and potassium compounds play major roles in chemical industries, glass production, and fertilizers; rubidium and cesium have niche research applications; francium is extremely rare and of primarily historical and scientific interest. Safety considerations reflect their high reactivity, requiring careful handling and appropriate storage.