Lithium (Li, Li) is a chemical element of the first group of the periodic table of elements of DI Mendeleev. Pore number 3, atomic weight (mass) 6.939, valence +1. 2 stable and 3 radioactive isotopes are known. Lithium is a component of plant and animal organisms. In humans, found in the lungs, liver, spleen, kidney, blood (mainly in plasma). Lithium is a soft, silver alkali metal, density 0.534, t ° pl 180 °. Lithium is chemically very active, it ignites in air (it is stored in lithium in paraffin oil) and forms alkali LiOH with water. Most lithium salts are well soluble in water. Volatile compounds of lithium paint the flame in carmine-red color. Apply lithium in alloys with other metals, in the production of glass, plastics, etc. Lithium salts (benzoate, citrate, chloride) are used in medicine. In the body, lithium is a sodium antagonist. Lithium compounds, introduced in amounts exceeding physiological concentrations, affect carbohydrate metabolism and tissue respiration. With long-term administration of large doses, lithium poisoning is observed: weakness, dizziness, damage to the gastrointestinal tract, slowing of cardiac activity. Treatment - an infusion of saline, glucose, diuretic and laxatives.