Lithium is a chemical element with the symbol Li. It is a soft alkali metal with a silver-white colour. Under standard conditions, it is the lightest metal and the least dense solid element. Like all alkali metals, lithium is highly reactive, corroding quickly in moist air to form a black tarnish. For this reason, lithium metal is typically stored under the cover of oil. Lithium salts such as lithium carbonate, lithium citrate, and lithium orotate are mood stabilizers. They are used in the treatment of bipolar disorder, since unlike most other mood altering drugs, they counteract both mania and depression. Lithium can also be used to augment other antidepressant drugs. It is also sometimes prescribed as a preventive treatment for migraine disease and cluster headaches. Side effects include muscle tremors, twitching, ataxia, hyperparathyroidism (bone loss, hypercalcemia, hypertension, etc,), kidney damage, nephrogenic diabetes insipidus (polyuria and polydipsia) and seizures. Many of the side-effects are a result caused by the increased elimination of potassium.