Explain the Modern Periodic Law and discuss the major defects of Mendeleev's Periodic Table that were successfully resolved by the Modern Periodic Table.

Q: Explain the Modern Periodic Law and discuss the major defects of Mendeleev's Periodic Table that were successfully resolved by the Modern Periodic Table.

Modern Periodic Law\nThe Modern Periodic Law was stated by Henry Moseley in 1913. It states that: "Properties of elements are a periodic function of their atomic number." This means that when elements are arranged in the increasing order of their atomic numbers, elements with similar properties recur after regular intervals. Resolution of Mendeleev's Periodic Table Defects\nHenry Moseley showed that atomic number is a more fundamental property of an element than its atomic mass. The arrangement based on atomic numbers resolved several anomalies in Mendeleev's Periodic Table: Position of Isotopes: Isotopes have the same atomic number but different atomic masses. In Mendeleev's table based on atomic mass, isotopes posed a problem for placement. In the Modern Periodic Table, since elements are arranged by atomic number, all isotopes of an element occupy the exact same position. Anomalous Pairs of Elements: In Mendeleev's table, certain pairs of elements with higher atomic masses were placed before those with lower atomic masses (e.g., Cobalt with atomic mass 58.9 was placed before Nickel with atomic mass 58.7) to group similar elements together. The Modern Periodic Table resolves this because Cobalt has an atomic number of 27 and Nickel has 28, meaning Cobalt correctly precedes Nickel based on increasing atomic number. Periodic Properties and Electronic Configuration: The Modern Periodic Table explains why elements show periodicity in properties. Elements in the same group have the same number of valence electrons in their outermost shell, leading to similar chemical behavior, whereas Mendeleev could not provide a fundamental reason for periodicity. Separation of Metals and Non-Metals: The Modern Periodic Table clearly segregates metals, non-metals, and metalloids with the help of a zig-zag line, providing a much more systematic classification compared to the older table.

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Modern Periodic Law
The Modern Periodic Law was stated by Henry Moseley in 1913. It states that: "Properties of elements are a periodic function of their atomic number." This means that when elements are arranged in the increasing order of their atomic numbers, elements with similar properties recur after regular intervals. Resolution of Mendeleev's Periodic Table Defects
Henry Moseley showed that atomic number is a more fundamental property of an element than its atomic mass. The arrangement based on atomic numbers resolved several anomalies in Mendeleev's Periodic Table: Position of Isotopes: Isotopes have the same atomic number but different atomic masses. In Mendeleev's table based on atomic mass, isotopes posed a problem for placement. In the Modern Periodic Table, since elements are arranged by atomic number, all isotopes of an element occupy the exact same position. Anomalous Pairs of Elements: In Mendeleev's table, certain pairs of elements with higher atomic masses were placed before those with lower atomic masses (e.g., Cobalt with atomic mass 58.9 was placed before Nickel with atomic mass 58.7) to group similar elements together. The Modern Periodic Table resolves this because Cobalt has an atomic number of 27 and Nickel has 28, meaning Cobalt correctly precedes Nickel based on increasing atomic number. Periodic Properties and Electronic Configuration: The Modern Periodic Table explains why elements show periodicity in properties. Elements in the same group have the same number of valence electrons in their outermost shell, leading to similar chemical behavior, whereas Mendeleev could not provide a fundamental reason for periodicity. Separation of Metals and Non-Metals: The Modern Periodic Table clearly segregates metals, non-metals, and metalloids with the help of a zig-zag line, providing a much more systematic classification compared to the older table.

MP Board · Class 10 · Science · Periodic Classification of ElementsExplain the Modern Periodic Law and discuss the major defects of Mendeleev's Periodic Table that were successfully resolved by the Modern Periodic Table.

Resolution of Mendeleev's Periodic Table Defects\nHenry Moseley showed that atomic number is a more fundamental property of an element than its atomic mass. The arrangement based on atomic numbers resolved several anomalies in Mendeleev's Periodic Table: