This paper addresses the conceptual as well as social origins of Mendeleev’s discovery of the periodic law and its reception by the chemical community by taking account of three factors: Mendeleev’s early research and its relevance to the discovery; his concepts of chemistry, especially that of the chemical elements; and the social context of the discovery and the reception in the chemical community. Mendeleev's clear distinction between abstract elements and simple bodies was a departure from Lavoisier’s famous definition of elements (...) as an endpoint of analysis and originated from his research in indefinite compounds. As a comparison, the paper also analyzes Lothar Meyer’s approach to the classification of the elements. Mendeleev’s new concept of chemical elements and the existence of an audience in the form of the newly established Russian Chemical Society, and his ``German connection'', helped Mendeleev in his discovery and its reception. (shrink)