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The Dawn of the Atom
Chances are, you’re not like me: you cringe when someone says the word “chemistry.” Your memory of it vaguely harkens back to an undergrad class whose knowledge you flushed once you finished the final. That’s okay — my goal for this series is to change that paradigm, make it understandable to all, and provide some entertainment.
With phlogiston and the four classical elements relegated to mythology, the stage was set for the creation and advancement of knowledge in chemistry. I realize that “creation of knowledge” is a phrase that most don’t encounter in their daily lives, and it begs the question, what does that even mean? For my purposes, I’ll define it as the discovery of time-tested, critical concepts, theories, ideas, etc. still in use today.
The Law of Definite Proportions
One of the first concepts that is a critical foundation for chemistry that we (“we” being chemistry instructors) typically gloss right over is the law of definite proportions. This law states very simply that given a pure substance, its constituent components will combine in definite, constant proportions no matter the source or method of preparation. For example, the law of definite proportion states that carbon dioxide will always derive 27% of its mass from carbon and 73% of its mass from oxygen no matter where it came from. This concept was later rebranded into atomic terms (i.e., instead we say carbon dioxide will always contain one atom of carbon and two atoms of oxygen), and that’s essentially how we teach it now. It seems like common sense, but when Joseph Proust originally proposed it in 1799, it was very much under serious debate, specifically with more famous chemist, Claude Berthollet — a disciple of Lavoisier and co-author of the new chemical naming system.
Proust, while not nobility, was still pretty well off as the son of a pharmacist. He was educated in Paris and spent his life in chemistry despite a small interruption from Napoleon. His investigations on definite proportions started chemists down the path of discovering the atom. To be more explicit, he defined the differences between compounds (substances containing more than one element that follow the law of definite proportions), mixtures (combined substances — but not chemically — and, therefore, don’t follow the law of definite proportions)…
