chemicalsolitaireactivity2015 - Name Partners Its in the Cards Discovering the Periodic Law Introduction Dmitri Mendeleevs discovery of the Periodic law

chemicalsolitaireactivity2015 - Name Partners Its in the...

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Name: ________________________ Partners: ________________________________ & ________________________________ It’s in the Cards Discovering the Periodic Law Introduction: Dmitri Mendeleev’s discovery of the Periodic law ranks as one of the greatest achievements in the history of science. It has survived the test of time and stands to this day as the single most important tool to understand the chemistry of the elements. As we try to understand the essence of this great discovery, it is worthwhile to go back in time and look at how it was achieved. What did Mendeleev know and when did he know it? Concepts: Periodic Law Periodic Table Atomic Mass Ionization Energy Background: In the years 1868-1870, Dmitri Mendeleev, a professor of chemistry at the University of St. Petersburg in Russia, was intent on writing a new textbook of chemistry, called Principles of Chemistry . More than 60 individual elements were known, and great many facts had been discovered about their properties and compounds. Mendeleev knew the atomic masses of the elements, their densities, boiling points, melting points, the formulas of their compounds with hydrogen, oxygen, and chlorine, and many other isolated facts. What was missing was a way to organize these facts, a way to understand how individual facts related to each other- in short, a way to classify the elements. The following quote is translated from Mendeleev’s first published report of the periodic law: “I wished to establish some sort of system of elements in which their distribution is not guided by chance…but by sort of definite and exact principle.” Mendeleev decided to arrange the elements systematically according to their atomic mass. He wrote out the exact atomic masses (as they were known at the time) in the margin of a list of the elements, and then wrote out separate cards for each of
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