Definition of the word valency

The term "valency" originated from the German word "Wertigkeit," meaning "value" or "worthiness," in the context of chemistry. It was introduced in the late 19th century by the German chemist Friedrich August Kekulé to describe the combining capacity of an atom in a chemical compound, i.e., the number of chemical bonds it can form with other atoms. The concept of valency was further developed by the Russian chemist Dmitri Mendeleev, who used it in his creation of the periodic table, which placed elements with the same valency in the same group. Mendeleev's periodic table, published in 1869, not only facilitated the discovery of new elements but also predicted the properties of unknown elements based on their valency. It became the foundation for modern chemistry and continues to serve as a fundamental tool in understanding the chemical behavior of elements. In summary, the term "valency" came from the German "Wertigkeit," meaning "value" or "worthiness," and was introduced in chemistry in the late 19th century to describe the combining capacity of an atom in a chemical compound, which allowed for a better understanding and organization of the chemical properties of elements.