Mendeleev's Prediction: Eka-Aluminium

Dmitri Mendeleev, a Russian chemist, is renowned for developing the periodic table of elements. While arranging the known elements based on their atomic masses and chemical properties, he observed patterns that led him to propose the periodic law.

The Periodic Table and Gaps

A significant aspect of Mendeleev's periodic table was his bold decision to leave gaps for elements that he predicted must exist but had not yet been discovered. He based this on the idea that his table was a fundamental representation of elemental relationships, and deviations or missing spots indicated undiscovered substances.

Naming Undiscovered Elements

To name these predicted elements, Mendeleev used a systematic approach based on Sanskrit prefixes. He prefixed the name of the element immediately preceding the predicted element in the same group with 'Eka' (meaning 'one' in Sanskrit). He also used 'Dvi' ('two') and 'Tri' ('three') for elements two or three places below.

The Case of Eka-Aluminium

• Mendeleev noticed a gap in his table under the element Aluminium (Al), which belongs to Group 13 (or IIIA in his notation).
• He predicted that an element with properties similar to Aluminium should exist below it.
• Following his naming convention, he called this predicted element Eka-Aluminium.

Mendeleev further predicted the properties of Eka-Aluminium, such as its atomic mass (around 68), density, and melting point. Later, in 1875, the element Gallium (Ga) was discovered, and its properties closely matched Mendeleev's predictions for Eka-Aluminium. Thus, Eka-Aluminium is the historical name given to the element Gallium before its discovery.