Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Erwin Madelung (May 18, 1881, Bonn August 1, 1972, Frankfurt/Main) was a German physicist. He was born in 1881 in Bonn. His father was the surgeon Otto Wilhelm Madelung. He earned a doctorate in 1905 from the University of Göttingen, specializing in crystal structure, and eventually became a professor. It was during this time he developed the Madelung constant, which characterizes the net electrostatic effects of all ions in a crystal lattice, and is used to determine the energy of one ion. In 1921 he was appointed head of theoretical physics at the University of Frankfurt/Main, which he held until 1949.