Antonius van den Broek (4.05.1870-25.10.1926) — Dutch lawyer and physicist, a member of the Royal Netherlands Academy of Arts and Sciences (1923). Born in Zoetermeer. He studied (1889–95) at the universities of Leiden and Paris. In 1895 he took the degree of doctor of law at the University of Leiden. In 1903–07 his interests shifted to the natural sciences, and in 1907 his first paper on physics appeared. His later research was mainly on the structure of the nucleus, the periodic table of the chemical elements and isotopy. In 1913 he put forward the hypothesis that the charge of an atomic nucleus is equal to the atomic number of the element, and a hypothesis that atomic nuclei are built of protons and electrons.