📝 Multiple Choice Question
General-science
When Mendeleev started his work, how many elements were known at that time?
A
56
B
61
C
63
D
72
Explanation
When Dmitri Mendeleev formally presented his groundbreaking periodic table to the Russian Chemical Society in exactly 1869, there were only 63 known elements. He boldly left strategic gaps for undiscovered ones, correctly assuming the list was incomplete.
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