Imagine trying to organise all the chemical elements known in the 19th century without knowing about protons, neutrons or electrons. This was the challenge faced by Russian chemist Dmitri Mendeleev.
In 1869, while working on his chemistry textbook, Mendeleev began arranging the known elements according to their atomic weights and chemical properties. He noticed that certain properties appeared to repeat in a regular pattern.
What made his work remarkable was that Mendeleev left gaps in his table for elements that had not yet been discovered. He even predicted their properties. Later discoveries, including gallium, scandium and germanium, closely matched his predictions and helped establish the significance of his periodic system.
The periodic table is more than a chart of chemical elements. It is a way of understanding how elements relate to one another through their properties and behaviour. Mendeleev’s work in 1869 helped establish this systematic approach, revealing patterns that could be used not only to organise known elements but also to anticipate the existence and properties of elements yet to be discovered.
