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
Dmitri Mendeleev developed an approach for organizing the elements while playing a game 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