The Evolution of Periodic Table: From Mendeleev to Modern
The periodic table is one of the most strikingly organized scientific models in the world, which manifests the arrangement of all known elements in the order of their atomic number, electron configuration, and chemical properties. The modern periodic table has evolved over time, from the earliest attempts by Dmitri Mendeleev to the most recent updates by the International Union of Pure and Applied Chemistry (IUPAC). In this article, we will explore the difference between Mendeleev’s periodic table and the modern periodic table.
Mendeleev’s Periodic Table
Dmitri Mendeleev, a Russian chemist, is often considered the father of the periodic table. In 1869, Mendeleev constructed his periodic table by arranging the known elements in order of increasing atomic mass. He arranged the elements in vertical columns called groups, which had similar chemical properties. The horizontal rows were called periods, and each period contained elements with properties that changed gradually from left to right.
Mendeleev left some spaces in his periodic table, suggesting that there were yet-to-be-discovered elements that would fill those gaps. He also arranged the elements according to their properties, correctly predicting the characteristics of the yet-to-be-discovered elements.
However, Mendeleev’s periodic table had some flaws. The atomic mass of some elements didn’t match their assumed positions based on their chemical properties. That’s the reason why some elements such as iodine and tellurium were placed in the wrong group. This discrepancy led to Mendeleev’s unsuccessful prediction of the properties of the rare gases.
Modern Periodic Table
The modern periodic table rectified the flaws of Mendeleev’s periodic table. In 1913, Henry Moseley, an English physicist, suggested that the atomic number could replace atomic mass as the basis of building the periodic table. At that time, the understanding of atomic structure improved, and it became clear that the atomic number was a more accurate representation of the number of protons in the nucleus of an atom.
The modern periodic table is arranged in increasing order of atomic number, with elements in the same group having similar electronic configuration and chemical properties. The modern periodic table has seven horizontal rows called periods and 18 vertical columns called groups.
Modern periodic table has more precise predictive power than Mendeleev’s table because it is based on the actual order of atomic numbers and it accurately places elements in the appropriate groups based on their electronic configurations. The modern periodic table includes all the discovered elements, and it provides a framework for organizing, predicting, and explaining the behavior of atoms.
Conclusion
In conclusion, the periodic table has come a long way since its inception by Dmitri Mendeleev, with the periodic table undergoing significant changes as our understanding of the elements and atomic structure has increased. Mendeleev’s periodic table was the first to organize the elements based on their chemical properties, but the modern periodic table is more precise and accurate, as it is based on atomic number rather than atomic mass. In brief, the modern periodic table is a more refined version of Mendeleev’s periodic table, which accurately represents the organization and behavior of all known elements.
Table difference between mendeleev and modern periodic table
| Aspect | Mendeleev Periodic Table | Modern Periodic Table |
|---|---|---|
| Arrangement of elements | Elements were arranged based on their increasing atomic mass. | Elements are arranged based on their increasing atomic number. |
| Gaps in the periodic table | Mendeleev predicted the existence of additional elements based on the gaps in the periodic table. | The modern periodic table does not have gaps as all known elements are included. |
| Number of elements | The Mendeleev periodic table had 63 elements. | The modern periodic table has 118 elements. |
| Properties of elements | Mendeleev arranged elements based on their physical and chemical properties. | The modern periodic table also arranges elements based on their chemical and physical properties but uses a more scientific basis. |
| Use of atomic number | The Mendeleev periodic table did not include atomic numbers as they were not yet discovered. | The modern periodic table uses atomic numbers to arrange elements. |