Jöns Jacob Berzelius

Born in 1779, Berzelius trained as a physician but pivoted to chemistry and joined the Royal Swedish Academy of Sciences in 1808, eventually running it from 1818 onward. He worked as a strict empiricist, developing better methods of chemical analysis to nail down atomic weights and the quantitative rules of how elements combine - what became the Law of Constant Proportions. He used electrochemical cells to split compounds, leading him to a theory of electrochemical dualism: that compounds were oxide salts held by electrostatic force, a framework later outgrown but pivotal at the time. Along the way he discovered cerium and selenium, isolated silicon and thorium, coined the terms for isomerism, allotropy, and catalysis, and created the system of one- or two-letter element abbreviations with superscripts for quantity - the notation that, switched to subscripts, every chemist uses today. He died in 1848, known in Sweden as the Father of Swedish Chemistry.