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

The Periodic Table Ch 5.1 – Finding Order

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.

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.

Mendeleev’s Periodic Table Mendeleev’s Proposal 1869 - 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

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

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

Mendeleev’s Periodic Table

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.

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.

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

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.

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

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

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

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

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

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.

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

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