The “father of modern chemistry” was the French chemist Lavoisier,¹ the son of a prominent advocate, born to a wealthy family in Paris. At Lavoisier’s time, chemistry was so underdeveloped it could hardly be called a science. The main view of combustion, or burning, was that of the “Phlogiston Theory,” which stated that certain materials contain a fire-like element called “Phlogiston,” which was liberated by burning; conversely, when those materials were heated, the “phlogiston” entered the material. One major problem with this theory was that, when some metals such as magnesium (which were considered to be rich in phlogiston) were oxidized, the resulting oxidized metal was heavier than the initial metal even though it was supposed to have lost weight. Lavoisier disproved the phlogiston theory by showing that combustion required a gas, oxygen, which had a weight. In a paper titled “Memoir on Combustion in General,” he presented his theory that combustion was a reaction in which oxygen combines with other elements. A simple example is the combustion reaction between hydrogen and oxygen (Fig. 8.1).

Lavoisier also discovered that, in a chemical reaction, matter is neither created nor destroyed, known as the “law of conservation of matter” (the mass of the reactants equals the mass of the products). For the first time, he formulated chemical reactions in the form of chemical equations based on the conservation of mass. Lavoisier was among the first to have a clear concept of a chemical element and the first to list the known elements. He was also the first to develop a rational system for naming chemical compounds. For these reasons, he is known as the father of modern chemistry. Due to his prominence in the pre-revolutionary government in France, this famous scientist was guillotined during the revolution. Today, statues of Lavoisier can be found in the city hall or the Louvre in Paris (Fig. 8.2).