Which discovery caused a revision in the periodic law as stated by Mendeleev?
Correct answer: B. Atomic number by Moseley
- A. Location of nucleus by Rutherford
- B. Atomic number by Moseley
- C. X-rays by Roentgen
- D. Natural radioactivity by Henry Becquerel
Explanation
While Mendeleev successfully organized elements based on their atomic mass, some anomalies and inconsistencies existed in his periodic table. The discovery of atomic number by Henry Moseley in 1913 provided a more fundamental basis for ordering elements. Moseley demonstrated that elements should be arranged in ascending order of their atomic number (number of protons), leading to a more accurate and predictive periodic table. This revelation rectified the inconsistencies in Mendeleev's system and cemented the atomic number as the primary organizing principle.
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About Periodic Properties and Trends
Periodic properties arise from electron configuration and effective nuclear charge, producing trends in atomic and ionic radius, ionization energy, electron affinity, electronegativity, metallic character and reactivity. Comparisons run across periods and down groups, with attention to common exceptions. The topic also relates these trends to the behavior of s-block and p-block elements.
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