Lithium and drugs
Lithium, of electronic structure 1 s2 2 s1, exists in two isotopes, one of mass 6, present at 8%, the other of mass 7, present at 92%. It is an alkaline element very easily ionizable. Its covalent radius is 1.34 Angström and its ion radius 0.60 Angström, very close to that of the Mg2+ ion which is doubly charged.
The quantity of lithium normally present in the body is extremely low, its plasma concentration is about 1 microgram per liter but it increases after ingestion and especially in the case of treatment where it reaches 0.5 to 0.8 mmol/L (1 mmole = 7 mg).