Reading Selection, Lesson 21
Dmitry's Card Game
It's interesting how different skills can be brought together to contribute to scientific discovery. Consider the story of Dmitry Mendeleyev and his card game that changed the face of chemistry.
Mendeleyev was a Russian college professor who loved to play cards. He was also looking for a way to organize the elements. To accomplish this, he wrote the symbols, characteristic properties, and other information for 63 elements on cards (only 63 elements had been discovered by 1869, the year he developed the card game). He then placed the cards face up on a table and began moving them around. He put the elements into groups according to the information he had about each one and how one element compared with another. For example, the elements sodium and potassium are soft, shiny, and highly reactive metals. Mendeleyev placed the cards for these elements in a column. He noticed that the elements calcium and magnesium had properties similar to one another, so he placed them together in another column. He did this with other elements and then moved the columns around so that the columns with similarities were next to one another. He discovered that when he did this, he could see patterns emerging. As he examined the rows of the table, he noticed that the pattern of properties periodically repeated itself. Thus, he called this classification system the “Periodic Table of the Elements.”
Over a period of 20 years, Mendeleyev improved his classification system. There were some gaps in the table—missing cards. He predicted that elements yet to be discovered would fill these gaps. He was able to suggest some of the characteristic properties they would have. As scientists became more knowledgeable about the physics and chemistry of matter, they helped refine the table, and the missing elements were discovered.
The periodic table was not the work of one person. As with most discoveries, evidence was collected over many years and scientists in many different countries were involved. Use the Internet and other resources to find out about the most famous scientists involved in developing the periodic table.