Mendeleev's predicted elements facts for kids

In 1869, a smart scientist named Dmitri Mendeleev created the very first periodic table of chemical elements. He put the elements in order from the lightest to the heaviest. When he first showed his table, he left some empty spots. He believed these spaces were for elements that had not been found yet. Mendeleev even guessed what these undiscovered elements would be like! He predicted their properties before anyone ever saw them.

Naming Undiscovered Elements

Mendeleev gave temporary names to the elements he thought were missing. He used special prefixes from the Sanskrit language: eka-, dvi-, and tri-. These mean 1, 2, and 3. He combined these prefixes with the name of a known element that was in the same group on the periodic table.

The prefix depended on how many rows away the known element was from the unknown one. For example, germanium was called eka-silicon. This is because silicon is one row above germanium. Rhenium was called dvi-manganese because manganese is two rows above rhenium. Once these elements were actually found, their names were changed to their official ones.

Other scientists also used the eka- prefix for elements Mendeleev didn't specifically predict. Before francium was discovered, it was called eka-caesium. Before astatine was found, it was called eka-iodine. The eka- prefix was also used for transuranic elements. These are elements that come after uranium on the periodic table. For example, ununoctium was sometimes called eka-radon. Element number 139, called untriennium, was also known as eka-actinium.

Today, the IUPAC has a different way to give new elements temporary names. This new method uses a systematic element name based on the element's atomic number. It does not depend on where the element is placed on the periodic table.