Introduction to the Periodic Table
Development of the Periodic Table
Describe the history of the peri- odic table.
Interpret an element key.
Explain how the periodic table is organized.
The periodic table makes it easier for you to find information that you need about the elements.
Review Vocabulary element: a substance that cannot be broken down into simpler substances
Early civilizations were familiar with a few of the substances now called elements. They made coins and jewelry from gold and silver. They also made tools and weapons from copper, tin, and iron. In the nineteenth century, chemists began to search for new elements. By 1830, they had isolated and named 55 different ele- ments. The list continues to grow today.
Mendeleev’s Table of Elements A Russian chemist, Dmitri Mendeleev (men duh LAY uhf), published the first ver- sion of his periodic table in the Journal of the Russian Chemical Society in 1869. His table is shown in Figure 1. When Mendeleev arranged the elements in order of increasing atomic mass, he began to see a pattern. Elements with similar properties fell into groups on the table. At that time, not all the elements were known. To make his table work, Mendeleev had to leave three gaps for missing elements. Based on the groupings in his table, he predicted the properties for the missing elements. Mendeleev’s predictions spurred other chemists to look for the missing elements. Within 15 years, all three elements—gallium, scandium, and germanium—were discovered.
Figure 1 Mendeleev published his first periodic table in 1869. This postage stamp, with his table and photo, was issued in 1969 to commemorate the event. Notice the question marks that he used to mark his prediction of yet-undiscovered elements.
K CHAPTER 4 The Periodic Table