Antoine Lavoisier named oxygen. He discovered that oxygen when combined with hydrogen (which he also named) produced water. He demonstrated oxygen’s role in rusting metal and in respiration. He proved the law of conservation of mass i.e. even though matter changed its state in a chemical reaction its mass remains unchanged. He discovered that air was a mixture of gases, primarily nitrogen and oxygen. He helped develop the metric system. He predicted that silica was likely an oxide of an unknown metal – later identified as the metalloid Silicon. He established that sulfur was an element and put together the first modern list of elements. These and other discoveries earned him the title “father of modern chemistry.”
Unfortunately Lavoisier was a nobleman and a member of the Ferme Générale – a group of unpopular feudal tax collectors. Being a liberal was no protection when you held a position marked for death during the French Revolution’s Reign of Terror. Jean-Paul Marat accused him of selling adulterated tobacco before his assassination. Lavoisier further compromised himself in the eyes of the Terror by protecting foreign born scientists from a mandate stripping foreigners of their possessions and freedom.
On May 8, 1794 Lavoisier was tried, convicted and guillotined.
A likely apocryphal story has the judge dismissing an appeal for mercy so that Lavoisier could continue his contributions to science with the words – “La République n’a pas besoin de savants ni de chimistes ; le cours de la justice ne peut être suspendu.” (“The Republic needs neither scientists nor chemists; the course of justice cannot be delayed.”)
Joseph Louis Lagrange, an Italian mathematician protected by Lavoisier, lamented the execution – “Cela leur a pris seulement un instant pour lui couper la tête, mais la France pourrait ne pas en produire une autre pareille en un siècle.” (“It took them only an instant to cut off his head, but France may not produce another such head in a century.”)
Less than two months after the execution of Lavoisier the Reign of Terror came to an end as Maximilien de Robespierre faced his own appointment with the National Razor. A year and a half after his death Lavoisier was exonerated by the French government which returned his private belongings “[t]o the widow of Lavoisier, who was falsely convicted.”