Modern Chemistry (20th Century Chemistry)- Mid 19th Century to Present
This is the era chemistry flourished. 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. (If you are using a graphical browser, there is a picture of Amedeo Avogadro to the left.) 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 element were very much alike in structure. Their work led Dmitri Mendeleev to publish the first periodic table. (If you are using a graphical browser, there is a picture of Dmitri Mendeleev on the the right.) 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 became 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 finalized the atomic theory. These and other major advanced in chemistry have led to many distinct branches of chemistry. These branches include, but are not limited to: biochemistry, nuclear chemistry, chemical engineering, organic chemistry.