ABOUT SCIENCE

Biography and Profile of Dimitri Mendeleev - The mid-nineteenth century was an exciting time in the history of chemistry. New elements were being discovered almost every year and innovative laboratory apparatus and techniques enabled chemists to look at matter in more detail than ever before. The most decisive moment in the history of chemistry occurred during this period of intellectual ferment. The discovery of unexpected patterns in nature the realization that order exists where none was previously seen is pivotal in the progress of science. Thus, when Dimitri Mendeleev developed the first periodic table and revealed the underlying order of the elements, he brought the science of chemistry into a new era of understanding.

Dimitri Mendeleev (1834-1907) was a popular chemistry professor at the Technological Institute of St. Petersburg in Russia. In 1869, he wrote the properties of the 63 known elements along with their atomic weights on small paper cards. He arranged the cards in various ways to see if he could find order among them; some say Mendeleev was inspired by the card game known as solitaire. By arranging the cards in order of increasing atomic mass as well as by their properties, he found a way to reveal one set of relationships when the cards were read up and down and another set of relationships when the cards were read side-to-side. Elements in the same column had similar properties for example copper, gold, and silver are all metals while helium, argon, and neon are all nonreactive gases. Across each horizontal row, were elements of repeating properties. Medeleev found however, that in order to align elements properly in a column, he had to shift elements right or left occasionally. This left gaps blank spaces that could not be filled in by any element. Instead of looking at the gaps as defects, Mendeleev predicted the existence of elements that had not yet been discovered.

In the years after the periodic table was published, more elements were discovered and gaps in Mendeleev’s table were filled in according to his predictions. The newly discovered elements had just the masses and properties anticipated. Of course, as more has been learned about atomic structure, Mendeleev’s original table has been modified and improved. But because it laid the groundwork for our understanding of atomic behavior in such a fundamental way, the periodic table is recognized as one of the most important achievements of modern science.

Conceptual Integrated Science