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Reading Selection, Lesson 21

Dmitry's Card Game

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Small line drawing of Mendeleyev

Dmitry Mendeleyev devised the forerunner to today's periodic table. Initially a poor student, he eventually graduated from college at the top of his class.

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.”

Color painting of an older Mendeleyev

Mendeleyev was 35 years old when he published his "Periodic Table of the Elements." This drawing shows him in his later years. Mendeleyev continued to hone his periodic table over the years.

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.

Early periodic table on yellowed paper

Mendeleyev's early "Periodic Table".

 

 

 

 

 

 

 

 

 

 

 

 

X-ray photograph of the sun

The periodic table is the "list of ingredients" for our entire universe. Most of the elements were formed in nuclear reactions, which took place inside stars or exploding stars called supernovas. Some of these nuclear reactions continue to take place inside our sun (shown in this X-ray photograph), which releases energy when the element hydrogen undergoes fusion and is converted to the element helium.

Question

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.

 

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