5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

5-1 The Search for order Why did they begin to organize the elements? How did they start the organization? Mendeleev's Periodic Table. Mendeleev’s Proposal How did he arrange it? What made him come up with the arrangement? Mendeleev’s Prediction Evidence Supporting Mendeleev’s table

Periodic songs and videos Tom Lehrer-Lobachevshy They Might Be Giants Harry Potter

In a video store, movies are in categories such as Action or Comedy 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.

Organizing the Elements The Search for Order Until 1750, scientists had identified only 17 elements, mainly metals, such as copper and iron. In 1789, Antoine Lavoisier grouped the known elements into categories he called metals, nonmetals, gases, and earths. For the next 80 years, scientists looked for different ways to classify the elements. But no system worked for all the known elements.

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.

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.

Mendeleev’s Proposal Elements in columns were organized by properties Within a column, the elements masses increased from top to bottom His chart was a periodic table- an arrangement of elements in columns, based on a set of properties that repeat from row to row. A calendar is another example of a periodic table

Mendeleev’s Prediction Mendeleev was able to offer the best explanation for how the properties of an element were related to its location in his table. When he placed the elements where their properties fit, there were several gaps in the table. He used the properties of elements located near the blank spaces in his table to predict properties for undiscovered elements.

Mendeleev’s Periodic Table Mendeleev was confident that the gaps in his table would be filled by new elements. Some scientists didn’t accept those predictions. Others used the predictions to help in their search for undiscovered elements.

Evidence Supporting Mendeleev’s Table The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be. Mendeleev named missing elements after elements in the same group. He named a missing element one space below aluminum eka-aluminum He predicted the properties to be A soft metal Low melting point Density about 5.9 g/cm3

In 1875, a French chemist discovered a new element and named it gallium (Ga) in honor of France. The properties were: is a soft metal, has a melting point of 29.7°C, and has a density of 5.91 g/cm3.

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.

Scientists use the periodic table to explain the chemical behavior of different groups of elements. The discovery of scandium (Sc) in 1879 and the discovery of germanium (Ge) in 1886 provided more evidence.

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.

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

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

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