Mendeleev's Periodic Table vs. Modern Periodic Table — What's the Difference?

In the context of Mendeleev's Periodic Table, it was Dmitri Mendeleev, a Russian chemist, who formulated this arrangement in 1869. He categorized elements based on their atomic masses and left spaces for those yet to be discovered, predicting their properties. On the other hand, the Modern Periodic Table has evolved significantly since Mendeleev's time. It organizes elements based on atomic number, not atomic mass.

Mendeleev's Periodic Table was groundbreaking for its time. Mendeleev's genius lay not just in organizing known elements but in forecasting the existence of elements that hadn't been discovered. This visionary approach set the foundation for future developments. In contrast, the Modern Periodic Table benefits from over a century of advancements in atomic theory and quantum mechanics. This has led to a more systematic arrangement, classifying elements into groups and periods according to their atomic number.

One distinguishing feature of Mendeleev's Periodic Table was its flexibility. Mendeleev sometimes positioned elements out of order by atomic mass to fit them into groups with similar properties. This intuitive approach was largely accurate, but not always precise. The Modern Periodic Table, with its emphasis on atomic number, has a more consistent and precise ordering system.

Mendeleev's Periodic Table was not universally accepted during his lifetime. He faced criticism and skepticism, but his predictions about undiscovered elements eventually proved correct, solidifying his legacy. The Modern Periodic Table, building on Mendeleev's foundation, has been refined through collaborative international efforts and is accepted universally today.

Another significant difference lies in the sheer number of elements. Mendeleev's Periodic Table had gaps, anticipating future discoveries. The Modern Periodic Table has grown to include all known elements, with spaces for possible future elements at its end.