Sort, Stack, Organize: How Mendeleev Created the Periodic Table
The UN made 2019 the International Year of the Periodic Table of Chemical Elements. But why do we need to celebrate this colorful chart? Let's take a look at its amazing discovery and history.
In 1869, Dmitry Mendeleev worked as a chemistry professor at the University of St. Petersburg. He was writing a chemistry textbook for his students. Mendeleev wanted to put all the known elements into some kind of order.
At that time, scientists had only identified around 60 elements. As a distinguished chemist, Mendeleev knew all their relative atomic weights. He also knew a lot about their chemical properties.
He wrote everything he knew about each element on a card. Then he tacked the cards up on a wall.
Mendeleev kept moving his cards around for almost a year. He was searching for a logical order.
Tactile learning, along with ordering and stacking can lead to great things!
Finally, Mendeleev hit upon the idea of putting Hydrogen, the lightest element, in first place in the upper left. Mendeleev started arranging all the known elements by increasing atomic weights.
As he did this, he found families of elements with similar chemical properties. Other patterns started to become evident.
For example, metals and nonmetals formed groups on opposite sides of Mendeleev's chart. Mendeleev started putting elements with similar properties into matching columns.
When he did this, he found he needed to leave gaps in his table. He predicted these gaps would be filled with elements that had yet to be discovered.
In this way, Mendeleev's gaps predicted the chemical properties of yet-to-be-discovered elements. By 1875, scientists had discovered three new elements. They fit into Mendeleev’s Periodic Table of elements perfectly.
Today, the Periodic Table contains 118 known elements. Every newly-discovered element fits into Mendeleev’s method of organization. The Periodic Table of Elements continues to expand and incorporate newly discovered elements.
The UN recognizes how the study of chemistry can help promote sustainable development. Chemists can provide solutions to global challenges in energy, education, agriculture, and health.
Thought of the day. Sorting, stacking, and organizing activities can be essential for understanding practical and theoretical concepts. Be like Mendeleev: use your sense of touch and appreciation of color to learn more and help others.
Who knows? By playing with cards or blocks -- you, too, can make a significant to contribution to unlocking the mysteries of the universe.