Jöns Jacob Berzelius (1779-1848) was a Swedish chemist. He worked out the modern technique of chemical formula notation, and is considered a father of modern chemistry. He began his career as a physician but his researches in physical chemistry were of lasting significance in the development of the subject. He is known in Sweden as the Father of Swedish Chemistry. In 1828 he compiled a table of relative atomic weights, where oxygen was set to 100, and included all of the elements known at the time. In order to aid his experiments, he developed a system of chemical notation in which the elements were given simple written labels, such as O for oxygen, or Fe for iron, with proportions noted by numbers. Berzelius is credited with identifying the chemical elements silicon, selenium, thorium, and cerium. Berzelius is also credited with originating the chemical terms "catalysis," "polymer," "isomer," and "allotrope," although his original definitions differ dramatically from modern usage.