How does a deck of cards and world map relate to the periodic table?

1. How does a deck of cards and world map relate to the periodic table?

2. The Periodic Table Ch 5.1 – Finding Order

3. The Search for Order • Until 1750 - • Only 17 elements had been identified • Mainly metals - such as copper and iron. • Alchemists • Natural abundance • As the number of known elements grew, so did the need to organize and present them in a universal manner.

4. The Search for Order • In 1789 - Antoine Lavoisier • Grouped the known elements into 4 categories • Metals • Nonmetals • Gases • Earths • For the next 80 years, scientists looked for different ways to classify the elements. But no system worked for all the known elements.

5. Mendeleev’s Periodic Table Mendeleev’s Proposal • 1869 - Dmitri Mendeleev developed an approach for organizing the elements while playing agame solitaire. • Making observations about how the cards were sorted (by suit and value) provided Mendeleev with an idea

6. Mendeleev’s Periodic Table • Mendeleev made a “deck of cards” of the elements • ~60 known elements • Listed on each card - an element’s • Name • Mass • Properties • Mendeleev lined up the cards in order of increasing mass • A new pattern emerged

7. Mendeleev’s Periodic Table • New Pattern • The key was to break the elements into rows. • Continued creating a row based on increasing mass until he came across an element with properties similar to those of one already in the row • Started a new row • Elements with similar properties were organized in columns

8. Mendeleev’s Periodic Table

9. Mendeleev’s Periodic Table • How did Mendeleev organize the elements in his periodic table? • He arranged the elements into rows in order of increasing mass so that elements with similar properties were in the same column.

10. Mendeleev’s Periodic Table • The final arrangement was similar to a winning arrangement in solitaire: • Columns were organized by properties (suits) • Within a column, the masses increased from top to bottom (value). • Trend – Mass Increases from left to right & top to bottom • Mendeleev’s chart became the 1st universal periodic table. • A periodic table is an arrangement of elements in columns, based on a set of properties that repeat from row to row.

11. Mendeleev’s Periodic Table Mendeleev’s Prediction • At the time Mendeleev made his table, many elements had not yet been discovered. • When he placed the elements where their properties fit, there were several gaps in the table. • Confident that gaps would be filled by NEW elements

12. Mendeleev’s Periodic Table Mendeleev’s Prediction • He used the properties of elements located near the gaps in his table to predict properties for undiscovered elements. • Able to offer the best explanation for how the properties of an element were related to its location in his table. • Some scientists didn’t accept those predictions. • Others used the predictions to help in their search for undiscovered elements.

13. 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 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 • have a density of 5.9 g/cm3

14. Evidence Supporting Mendeleev’s 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 • So low a persons body heat will melt it • has a density of 5.91 g/cm3

15. Evidence Supporting Mendeleev’s Table • The discovery of other elements and their properties provided even further evidence to support Mendeleev’s design. • Scandium (Sc) in 1879 • Germanium (Ge) in 1886 • Today scientists use the periodic table to explain the chemical behavior of different groups of elements

16. Assessment Questions 1. How many elements were discovered between1750 and the 1869? • ~20 • ~40 • ~30 • ~60

17. Assessment Questions 2. Following his observations, Mendeleev began organizing the elements by lining them up in order of • Decreasing mass • Increasing atomic number • Increasing mass • Increasing melting point

18. Assessment Questions 3. 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.

19. Assessment Questions 4. Mendeleev made predictions regarding the gaps in his table by • Using only the masses of the surrounding known elements • Using the known elements subatomic particles • Using only the known elements melting points • Using all the various properties of the known elements surrounding the gaps

20. Assessment Questions 5. For which element did Mendeleev correctly predict the properties even before it had been discovered? • gallium • hydrogen • bromine • aluminum