The atomic mass of the middle element is the average of the atomic masses of other two elements. This is a statement of
Correct answer: D. Dobereiner
- A. Lothar Meyer
- B. A.E. de Chancourtois
- C. Newlands
- D. Dobereiner
Explanation
The correct answer is Dobereiner. Johann Wolfgang Döbereiner proposed the concept of 'triads' in which groups of three elements have similar chemical properties, and the atomic mass of the middle element is the average of the atomic masses of the other two. This was an early attempt to find a pattern in the atomic masses before the development of the modern periodic table. The other options are incorrect because they refer to individuals who contributed to the periodic table in different ways but did not specifically propose the idea of triads. Lothar Meyer focused on atomic volume and atomic weight, A.E. de Chancourtois on the telluric helix, and Newlands on the Law of Octaves.
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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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