(August 9, 1776 – July 9, 1856)
Avogadro died exactly one month before his 80th birthday, which was also a day before Nikola Tesla was born. Like some great scientists before him, this physics professor studied religion and law before opting for science. And just like his compatriot, Alessandro Volta, who cashed-in on what eluded Luigi Galvani, Avogadro explored facts which Joseph Louis Gay-Lussac overlooked, alongside those that stumped John Dalton. This resulted in his contributions to Molecular Theory. His famous hypothesis (sometimes called law) propelled Physical Chemistry to loftier heights. This is noteworthy because the terms “atom” and “molecule” were used interchangeably in his era. Avogadro was indeed the person who fostered the term “molecule”. His works were so ahead of their time that his contemporaries showed little interest in them. Notwithstanding, they ushered-in our contemporary age of Particle Physics. It was after André-Marie Ampère rediscovered few of them, that scientists gave them second thoughts. Organic Chemistry experiments, which Auguste Laurent and Charles-Frédéric Gerhardt subsequently conducted, supported Avogadro’s claim that (at constant temperature and pressure) equal volumes of all gases contain equal numbers of molecules. However, he was already deceased, when (in 1860) Stanislao Cannizzaro reenacted and detailed the greatness of his research. They not only helped to determine atomic and molecular masses, but reconciled Dalton’s and Gay-Lussac’s postulations. Several years would elapse before the depths of his accomplishments were fully appreciated: and they consolidated his status as a founder of Molecular Theory. The Avogadrite mineral, and 139-kilometer-wide Avogadro lunar crater, are dedicated to him.