Chapter 3Introduction to the Periodic

Table

Section 3.1 Development of the Periodic TableSection 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.

Review1. Döbereiner arranged his elements in

groups of how many elements? This grouping was based on what information?

2. Mendeleev predicted the properties of what two undiscovered elements?

3. What led to the wide spread acceptance of Mendeleev’s table?

4. Sodium and Potassium react violently with water. How would you expect Rubidium to react with water?