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The modern periodic law arranges elements in order of:
AAtomic mass, the criterion used by Mendeleev in 1869
BAtomic number, the criterion settled after Moseley's work
CDensity, with heavier elements lower on the chart
DDiscovery date, in chronological order of element finding
Answer & Solution
Correct answer: B. Atomic number, the criterion settled after Moseley's work
The modern law: properties are a periodic function of atomic number, not mass.
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