The book is part of a series devoted to the disclosure of the fundamental law of nature - the periodic law and a review of elements by groups of the periodic table of chemical elements. The book is devoted to the elements of group II of the periodic system, describes their properties, as well as their compounds, the history of discovery, distribution and nature and application in the national economy. The title of the book is due to the fact that alkaline earth metals as simple substances were isolated using electric current.