According to The Third Millennium Online, Antoine-Laurent de Lavoisier’s thesis gave chemists the first sound understanding of the nature of chemical reactions. Lavoisier’s work led an English schoolteacher by the name of John Dalton to formulate his atomic theory. Around the same time an Italian chemist, Amedeo Avogadro, formulated his own theory, Avogadro’s Law, concerning molecules and their relation to temperature and pressure. By the middle of the 19th Century, there were approximately 60 known elements. John A.R. Newlands, Stanislao Cannizzaro and A.E.B. de Chancourtois first noticed that all of these elements were very much alike in structure. Their work led Dmitri Mendeleev to publish the first periodic table. Mendeleev’s work set the foundation of theoretical chemistry. In 1896 Henri Becquerel and the Curies discovered the phenomenon known as radioactivity. This laid the foundation for nuclear chemistry. In 1919, Ernest Rutherford discovered that elements could be transmutated. Rutherford’s work laid  the basis for interpreting the structure of the atom. Soon after, another chemist, Niels Bohr, finalised the atomic theory. These, and other major advancements in chemistry, have led to many distinct branches of chemistry. These branches include, but are not limited to: biochemistry, nuclear chemistry, chemical engineering, and organic chemistry. 

Antoine Lavoisier (1743-1794). He was a French chemist who made important contributions to the science. He is considered the father of modern chemistry. He recognised and named oxygen and isolated the major components of air. 

While working as a tax collector, Lavoisier helped to develop the metric system in order to insure uniform weights and measures. He was admitted to the French Academy of Sciences in 1768.

In that same year, he began to devote himself almost exclusively to chemical inquiries, and established a laboratory in his home, fitted with all manner of costly apparatus and chemicals. Here, he was in constant communication with the great men of science of Paris, to all of whom his doors were thrown open. One of his first undertakings in this laboratory was to demonstrate that water could not be converted into earth by repeated distillations, as was generally advocated; and to show also that there was no foundation to the existing belief that it was possible to convert water into a gas so "elastic” as to pass through the pores of a vessel. He demonstrated the fallaciousness of both these theories in 1768 to 1769 by elaborate experiments, a single investigation of this series occupying one 101 days.

Along with Lavoisier, Boyle, and Dalton, Berzelius is also known as the father of modern chemistry. In 1828, he compiled a table of relative atomic weights, where oxygen was set to 100, and which included all of the elements known at the time. This is according to online platform, Cosmovisions. 

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