Atoms, Molecules & Elements Gr. 5-8 by Graybill George;

Author:Graybill, George;
Language: eng
Format: epub
Publisher: Classroom Complete Press

The Periodic Table

Each element has its own chemical and physical properties. For hundreds of years, Scientists have tried to learn more about the elements by studying their properties.

Early scientists didn’t know much about atoms. They didn’t have the atomic model you studied earlier. They did know a little about the mass of atoms. They were able to arrange the elements in order from the atom with least mass to the atom with the most mass.

When they looked at this list, they saw something interesting. The properties of the elements repeated every so often. For example, the 4th, 12th, and 20th elements showed the same properties.

They arranged the elements in a table that showed how properties repeated. Each time the properties started to repeat, they started a new row of the table. This table is called the periodic table of the elements. The periodic table shown here is the one scientists use today.

The periodic table told scientists a lot about how each element would behave. It told them when to expect elements to form compounds. But they still didn’t understand why elements behaved the way they did. They also did not understand or why properties repeated.

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