Short answers, pulled from the story.
Antoine-Laurent de Lavoisier was a French nobleman and chemist central to the 18th-century chemical revolution. He discovered the role oxygen plays in combustion, opposed the phlogiston theory, and helped turn chemistry from a qualitative into a quantitative science.
Antoine Lavoisier showed that burning substances combine with part of the air rather than releasing a hidden principle called phlogiston. He named oxygen in 1778, from Greek words meaning "acid former," and recognized it as an element.
Lavoisier's law holds that matter may change its form in a chemical reaction while its total mass stays the same. In France it is taught as Lavoisier's Law, paraphrased from his words: "Nothing is lost, nothing is created, everything is transformed."
Antoine Lavoisier was guillotined in Paris on the 8th of May 1794, at the age of 50, alongside 27 co-defendants. As a member of the Ferme générale he was charged with defrauding the state and adding water to tobacco. A year and a half later the French government completely exonerated him.
In 1787 Lavoisier, with Guyton de Morveau, Berthollet, and Fourcroy, published the Méthode de nomenclature chimique, replacing the classical elements with about 33 substances listed as elements. The system named acids and salts by their oxygen content, turning "vitriol of Venus" into copper sulfate.
Marie-Anne Pierrette Paulze married Antoine Lavoisier in 1771 and became a renowned chemist in her own right. She translated English documents such as Richard Kirwan's Essay on Phlogiston, engraved the laboratory instruments, edited his memoirs, and helped develop the metric system of measurements.