20. Mendeleev's Table

Dmitri Mendeleev is a scientist in Russia. He loves studying chemistry. He wants to understand different elements, like hydrogen and oxygen.

One day, Mendeleev has a great idea. "I will make a table for the elements," he thinks. He writes the names of the elements on small cards. Each card has information about one element.

Mendeleev looks at the cards. He notices that some elements are similar. For example, some are metals, and some are gases. He begins to put the cards in rows and columns.

Mendeleev works hard. He wants to organize the elements. He puts them in order by their atomic weight. He makes a table that shows how the elements are related.

When he finishes, Mendeleev is happy. "This is my periodic table!" he says. He sees that the elements fit well together in the table.

Mendeleev also sees gaps in his table. Some elements are missing. "These elements will be discovered later," he thinks. He believes they exist.

His periodic table helps other scientists. They learn more about the elements. Mendeleev becomes famous for his work.

People remember him as a great scientist who helps change chemistry. His periodic table is important for many years.