Write the drawbacks in Mendeleev’s periodic table that led to its modification.

Mendeleev's periodic table, while groundbreaking and influential in the development of modern chemistry, had several drawbacks that eventually led to its modification and the development of the modern periodic table. Some of the key drawbacks include:

1. Use of Atomic Mass as the Organizing Principle: Mendeleev organized elements primarily by increasing atomic mass. While this arrangement generally worked well and allowed him to predict the properties of unknown elements, it led to inconsistencies and anomalies, such as the inversion of the order of certain elements to maintain similar chemical properties. Additionally, the discovery of isotopes and the inability to accurately measure atomic masses at the time caused some discrepancies in the arrangement.

2. Omission of Noble Gases: Mendeleev's periodic table did not include noble gases because they were not yet discovered at the time of its creation. As a result, the periodic table did not account for these elements with unique properties, such as their inertness and full valence electron shells.

3. Positioning of Hydrogen: Mendeleev faced challenges in determining the appropriate placement of hydrogen in the periodic table due to its unique properties. He ultimately placed hydrogen in Group 1 alongside alkali metals, even though hydrogen shares some similarities with Group 17 elements (halogens) as well.

4. Incompleteness and Gaps: The periodic table developed by Mendeleev contained gaps for elements that had not yet been discovered. While Mendeleev successfully predicted the properties of some of these missing elements, such as gallium and germanium, the periodic table was not fully comprehensive or systematic.

5. Limited Explanation of Periodicity: Mendeleev's periodic table provided a systematic arrangement of elements but did not offer a comprehensive explanation for the observed periodic trends, such as variations in atomic radius, electronegativity, and ionization energy across periods and groups.

6. Failure to Account for Electron Configuration: Mendeleev's periodic table did not consider the electronic configuration of atoms, which plays a crucial role in determining the chemical properties of elements. The modern periodic table organizes elements based on increasing atomic number and electron configuration, providing a more accurate representation of their properties and behavior.

Overall, while Mendeleev's periodic table laid the foundation for understanding the relationships between elements, its limitations and drawbacks necessitated the development of the modern periodic table, which is based on atomic number and provides a more systematic and comprehensive framework for organizing and studying the elements.