This book investigates the historical and scientific mystery surrounding the seven elements that remained missing from the periodic table after Henry Moseley established the concept of atomic number in 1913. Eric R. Scerri, a prominent historian and philosopher of science, utilizes primary source documentation and historical records to reconstruct the timeline of discovery for these elusive elements. The text argues that the identification of these substances was not merely a laboratory success but a complex interplay of geopolitical shifts, technological advancement, and theoretical physics during the early twentieth century.

Experts and historians of science frequently commend this work for its rigorous archival research and its ability to humanize the technical history of chemistry. Readers often note that the prose is accessible to those with a general interest in science while maintaining the academic depth required for professional historians.