Chapter 3 Introduction to the Periodic Table Section 3.1 Development of the Periodic Table Section 3.2 Using the Periodic Table

3.1 Development of the Periodic Table Objectives Outline the steps in the historical development of the periodic table. Predict the similarities of properties of elements by using the periodic table.

New Vocabulary to Look for… Periodicity Periodic law

Searching for a Periodic Table By 1860 scientists had discovered 60 elements and determined their atomic masses. They noticed that some elements had similar properties. Copper, Silver and Gold- coinage metals Lithium, Sodium and Potassium- alkali metals. Chlorine, Bromine and Iodine- halogens

Döbereiner’s Triads Chemists wanted to organize the elements into a system. Döbereiner was the first to classify some elements into groups of three. The halogen triad, metal triad Triads were useful Grouped elements with similar properties. Revealed an orderly pattern to some physical and chemical properties. Suggested properties were related to the atomic mass

Mendeleev’s Periodic Table Dmitri Mendeleev was a Russian chemist and professor. 1869 he published his first table of elements organized by atomic mass. Listed in vertical columns starting with the lightest. Elements with similar properties were placed in horizontal rows.

Mendeleev’s Periodic Table He later developed an improved version. Elements arranged in horizontal rows Forerunner to the modern periodic table. Patterns of changing properties repeated for the elements across the horizontal rows. Elements in the vertical columns showed similar properties.

Mendeleev His insight was a significant contribution to chemistry. He showed that properties of elements repeat in an orderly way from row to row of the table. Periodicity-the tendency to recur at regular intervals Mendeleev predicted the properties of undiscovered elements.

Mendeleev’s Predictions Called the elements eka-silicon and eka-aluminum. Based on their location on his table he predicted several of their properties. He was correct: Eka-aluminum was discovered in 1875 and called gallium Eka-silicon was discovered in 1886 and called germanium.

Mendeleev’s confidence He was so confident about his table that he placed some elements with groups with similar properties even though the atomic masses were not in order. Tellurium- he assumed the atomic mass was wrong. He was right on its placement, but wrong about the atomic mass

Modern Periodic Table It now has about 118 elements arranged in groups with similar properties. Transition elements, lanthanides, actinides and noble gases were unknown at Mendeleev’s time, but are found on today’s table.

Element Block

Periodic Law The statement that the physical and chemical properties of the elements repeat in a regular pattern when they are arranged in order of increasing atomic number.

Review Döbereiner arranged his elements in groups of how many elements? This grouping was based on what information? Mendeleev predicted the properties of what two undiscovered elements? What led to the wide spread acceptance of Mendeleev’s table? Sodium and Potassium react violently with water. How would you expect Rubidium to react with water?