5.1 organizing the elements 5-1 the search for order –why did they begin to organize the elements?...
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5.1 Organizing the Elements
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 Organizing the Elements
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 Organizing the Elements
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 Organizing the Elements
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 Organizing the Elements
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 Organizing the Elements
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 Organizing the Elements
Periodic songs and videos
• Tom Lehrer-Lobachevshy
• They Might Be Giants
• Harry Potter
5.1 Organizing the Elements
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.
5.1 Organizing the Elements
1. Until 1750, scientists had identified only 17 elements, mainly metals, such as copper and iron.
2. In 1789, Antoine Lavoisier grouped the known elements into categories he called metals, nonmetals, gases, and earths.
3. For the next 80 years, scientists looked for different ways to classify the elements. But no system worked for all the known elements.
I. Organizing the ElementsA. The Search for Order
5.1 Organizing the Elements
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
5.1 Organizing the Elements
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 Periodic Table
5.1 Organizing the Elements
a. Elements in columns were organized by properties
b. Within a column, the elements masses increased from top to bottom
c. His chart was a periodic table- an arrangement of elements in columns, based on a set of properties that repeat from row to row.
1) A calendar is another example of a periodic table
4. Mendeleev’s Proposal
5.1 Organizing the Elements
5. Mendeleev’s Prediction
a. Mendeleev was able to offer the best explanation for how the properties of an element were related to its location in his table.
b. When he placed the elements where their properties fit, there were several gaps in the table.
c. He used the properties of elements located near the blank spaces in his table to predict properties for undiscovered elements.
5.1 Organizing the Elements
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.
Mendeleev’s Periodic Table
5.1 Organizing the Elements
a. The close match between Mendeleev’s predictions and the actual properties of new elements showed how useful his periodic table could be.
b. Mendeleev named missing elements after elements in the same group.
1) He named a missing element one space below aluminum eka-aluminum
2) He predicted the properties to be
a) A soft metal
b) Low melting point
c) Density about 5.9 g/cm3
6. Evidence Supporting Mendeleev’s Table
5.1 Organizing the Elements
c. In 1875, a French chemist discovered a new element and named it gallium (Ga) in honor of France.
1) The properties were:a) is a soft metal,
b) has a melting point of 29.7°C, and
c) has a density of 5.91 g/cm3.
5.1 Organizing the Elements
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.
Mendeleev’s Periodic Table
5.1 Organizing the Elements
d. Scientists use the periodic table to explain the chemical behavior of different groups of elements.
1) The discovery of scandium (Sc) in 1879 and the discovery of germanium (Ge) in 1886 provided more evidence.
5.1 Organizing the Elements
Assessment Questions
1. In Mendeleev’s periodic table, elements with similar properties were grouped a. in the same row.
b. in the same column.
c. in diagonal lines that run from top left to the bottom right.
d. in pairs of two.
5.1 Organizing the Elements
Assessment Questions
1. In Mendeleev’s periodic table, elements with similar properties were grouped a. in the same row.
b. in the same column.
c. in diagonal lines that run from top left to the bottom right.
d. in pairs of two.
ANS: B
5.1 Organizing the Elements
Assessment Questions
2. For which element did Mendeleev correctly predict the properties even before it had been discovered?a. galliumb. hydrogenc. bromined. aluminum
5.1 Organizing the Elements
Assessment Questions
2. For which element did Mendeleev correctly predict the properties even before it had been discovered?a. galliumb. hydrogenc. bromined. aluminum
ANS: A