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Mendeleev's Periodic Table: Organizing Elements and Predicting Properties

Learn about Dmitri Mendeleev's approach to organizing elements in the periodic table and how he accurately predicted the properties of gallium even before its discovery. Discover the significance of grouping elements with similar properties and the impact of Mendeleev's periodic table in chemistry.

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Mendeleev's Periodic Table: Organizing Elements and Predicting Properties

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  1. In a video store, movies are in categories such as Action or Comedy. When scientists organized the elements, they had to decide what categories to use and where to place each element. An organized table of the elements is one of the most useful tools in chemistry.

  2. Mendeleev’s Periodic Table Mendeleev’s Proposal In the 1860s, Dmitri Mendeleev developed an approach for organizing the elements while playing the card game solitaire. In this game, the player sorts a deck of cards by suit and value.

  3. Mendeleev’s Periodic Table Mendeleev made a “deck of cards” of the elements, listing an element’s name, mass, and properties on each card. When Mendeleev lined up the cards in order of increasing mass, a pattern emerged. The key was to break the elements into rows.

  4. Mendeleev’s Periodic Table Mendeleev named missing elements after elements in the same group. He gave the name eka-aluminum to the missing element one space below aluminum in the table. Mendeleev predicted that eka-aluminum would • be a soft metal, • have a low melting point, and • have a density of 5.9 g/cm3.

  5. Mendeleev’s Periodic Table In 1875, a French chemist discovered a new element. He named the element gallium (Ga) in honor of France. (The Latin name for France is Gallia.) Gallium • is a soft metal, • has a melting point of 29.7°C, and • has a density of 5.91 g/cm3.

  6. Mendeleev’s Periodic Table Heat from a person's hand can melt gallium. In some traffic signals, there are tiny light emitting diodes (LEDs) that contain a compound of gallium.

  7. Assessment Questions • In Mendeleev’s periodic table, elements with similar properties were grouped • in the same row. • in the same column. • in diagonal lines that run from top left to the bottom right. • in pairs of two.

  8. Assessment Questions • In Mendeleev’s periodic table, elements with similar properties were grouped • in the same row. • in the same column. • in diagonal lines that run from top left to the bottom right. • in pairs of two.ANS: B

  9. Assessment Questions • For which element did Mendeleev correctly predict the properties even before it had been discovered? • gallium • hydrogen • bromine • aluminum

  10. Assessment Questions • For which element did Mendeleev correctly predict the properties even before it had been discovered? • gallium • hydrogen • bromine • aluminum ANS: A

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